=head1 UPGRADING FROM RT 4.4.0 and greater

The 5.0 release is a major upgrade and as such there are more changes
than in a minor bugfix release (e.g., 4.4.0 to 4.4.1) and some of these
changes are backward-incompatible. The following lists some of the notable
changes, especially those that might require you to change a configuration
option or other setting due to a change in RT. Read this section carefully
before you upgrade and look for changes to features you currently use.

See F<devel/docs/UPGRADING-5.0> for internals changes relevant to
extension writers, including deprecated code.

=head2 Upgrading Recommendations

RT now defaults to a database name of rt6 and an installation root of
/opt/rt6.

If you are upgrading, you will likely want to specify that your database is
still named rt4 or even rt3. Alternatively, you could import a backup of your
database as rt6 to conform to the new default, although this isn't required.

Upgrading to RT 5 over an existing RT 4 installation (/opt/rt4) is not
recommended and will almost certainly cause issues. Instead, do a fresh
install into /opt/rt6 (or your custom location) for the code portion of the
upgrade. Then import your existing database and run the database upgrade
steps using make upgrade-database.

We recommend this approach because of the large number of changes to the code
base for this major release. We moved some things to new locations and old
files are not removed as part of the upgrade process. These old files will
still be detected by RT in some cases and will cause issues.

Installing a fresh code base will also allow you to evaluate your local
modifications and configuration changes as you migrate to 5.0. If you have
changes made directly to the RT code, it's a good time to look at the hooks
RT provides for custom code in extensions or in the local directory. See
F<docs/writing_extensions.pod> for more information.

=head2 Database Changes

=over

=item *

For MySQL and MariaDB, the default character set has been updated to utf8mb4
to accommodate more unicode characters including emojis. See F<README.MySQL>
and F<README.MariaDB> for details.

=item *

The Id field in some tables is changed from INT to BIGINT to accommodate
large RT systems that may hit the maximum number of ids. Because this
change touches large RT tables like Transactions and Attachments, this
upgrade step may take a while to run.

You also will need free disk space equal to the size of these tables
while running because MySQL, MariaDB, and PostgreSQL will create a
temporary copy of the table while running. If you don't have sufficient
space, it can cause this step to fail.

=back

=head2 Notable Changes

=over

=item *

System configuration options can now be changed by SuperUsers via the
web UI. File-based configuration options are still loaded. Changes made
via the web UI take precedence over file-based options if both are set.

If you prefer to keep all configuration in files and disable editing in
the web UI, set this option to 0:

    Set($ShowEditSystemConfig, 0);

=item *

The variables which alter the set of HTML elements allowed in HTML
scrubbing have moved; they have been renamed, and are now found under
L<RT::Interface::Web::Scrubber>.

=item *

The articles interface on tickets has been simplified, now showing only
a dropdown for selecting articles. This dropdown converts to an autocomplete
box when the dropdown contains more than C<$DropdownMenuLimit> items.

With this simplified interface, the "hotlist" feature is no longer needed as
all articles in classes applied to a given queue are available in the
dropdown/autocomplete field. To prevent articles in a class from appearing
for a queue, you can unapply the class from that queue.

The upgrade steps remove the hotlist configuration from your RT database
by removing that column from the Articles table. Since the article class
must be applied to a queue for the hotlist items to appear, all articles
should continue to appear in the new interface.

=item *

The updated rich text editor now shows the browser context menu (right-click
menu) by default, so the MessageBoxUseSystemContextMenu configuration option is
no longer needed and has been removed.

=item *

Dashboards previously in the Home menu have been moved to the Reports menu.
The reports previously in the Reports menu are still there, but you can now
edit the Reports menu like the previous Home menu, so you can remove the
default reports if you like.

All other dashboard menu functionality should be the same including editing
your own menu, the global settings, and setting a user's menu from the user
admin page for that user.

=item *

Accessing RT from a mobile device no longer defaults to the mobile-optimized
interface. RT 5.0 is fully responsive so the full UI can be used on mobile
devices. Set the configuration option C<$ShowMobileSite> to true to restore
the previous behavior.

=item *

RT can now run with GnuPG 2.2. On install or upgrade, it requires the updated
version of L<GnuPG::Interface>. C<make testdeps> will test for the correct version.
RT should also still run with GnuPG 1.4.x. It is not supported for GnuPG versions
2.0 or 2.1. On some Linux systems, you may need to add a new repo to get an
updated GnuPG package with some version of 2.2.

=item *

RT search results now allow inline editing of ticket metadata, greatly
improving usability and convenience. Editable fields are now the default
for most ticket fields in search results.

The ticket Owner field sometimes requires extra work to build and can
result in slower page load times, so the default Owner format is
read-only. To enable inline edit for Owner, update your search to use
the format OwnerNameEdit.

If you experience slower page loads with OwnerNameEdit, you can
display Owner as an autocomplete box rather than a dropdown using the
L<AutocompleteOwners|https://docs.bestpractical.com/rt/4.4.4/RT_Config.html#AutocompleteOwners>
configuration option. This may also help other areas of RT in addition to
searches.

We are investigating options to improve the underlying queries. Some users have
reported improved performance with the following indexes, at least on PostgreSQL:

   CREATE INDEX ACL2 ON acl (objecttype, objectid);
   CREATE INDEX ACL3 ON acl (principalid, rightname, principaltype);

We are performing testing and looking for additional feedback before adding these
to default RT.

=back

=head2 Extensions Integrated into RT 5

The following extensions are now part of RT 5. If you previously used any as
an extension, you no longer need the extension after upgrading and can
remove the C<Plugin> line from your RT configuration.

Changes you may need to apply if you previously used the extension
are described below.

=over

=item RT::Extension::QuoteSelection

=item RT::Extension::RightsInspector

=item RT::Extension::ConfigInDatabase

If you previously used L<RT::Extension::ConfigInDatabase>
as an extension, run the F<etc/upgrade/upgrade-configurations> utility
after completing all the other upgrade steps from the F<README>. This
will migrate your existing configuration to the new core RT tables.

=item RT::Extension::CustomRole::Visibility

=item RT::Extension::PriorityAsString

If you previously used numbers for priority and would like to continue
to do so, you can set the new C<$EnablePriorityAsString> option to false.
That will disable the new string-based display.

We also now hide Final Priority by default, but if you previously used it
and would like to continue to do so, you can add this to the Custom CSS
section on the Theme editor:

    .FinalPriority, .TicketFinalPriority {
        display: flex;
    }
    .priority div.value .current-value {
        visibility: visible;
    }
    .priority div.value .current-value .FinalPriority {
        display: inline;
    }

If you would like to now use strings for priority like Low, Medium, High,
check the new C<%PriorityAsString> configuration option. RT provides a simple
default setting that may be sufficient. Set new values if you would like
to customize your priority options.

If you were previously using the PriorityAsString extension, you no longer
need the extension installed. The C<%PriorityAsString>> configuration is
simplified and consolidated, so check the documentation for details on
updating your previous configuration.

=item RT::Extension::AssetSQL

The configuration option $AssetSQL_HideSimpleSearch is now $AssetHideSimpleSearch.
The configuration option $AssetSearchFormat is now $AssetSimpleSearchFormat.

See the configuration documentation in L<RT_Config.pm> for new configuration
options added for AssetSQL and the new asset query builder.

=item RT::Extension::LifecycleUI

=item RT::Extension::REST2

=item RT::Authen::Token

If you previously used L<RT::Authen::Token|https://metacpan.org/pod/RT::Authen::Token>
as an extension, run the F<etc/upgrade/upgrade-authtokens> utility
after completing all the other upgrade steps from the F<README>. This
will migrate your existing tokens to the new core RT tables.

=back

=head1 UPGRADING FROM 5.0.0 AND EARLIER

=over 4

=item *

The extension C<RT::Extension::FormattedTransaction> was added to core. This
adds a new RT dependency on the Perl module L<Text::WordDiff>, so you will be
prompted to install this new module if your system doesn't have it.

=item *

Similar to the note above regarding the Owner field in search results,
custom fields in search results also now have inline edit enabled by default,
allowing you to change values directly in search results.

For heavy search result pages with many columns display or many rows,
page loads may be slower with this inline edit mode enabled. If you don't
need to edit custom field values, you can change search result columns
from C<CustomField.{Foo}> to C<CustomFieldView.{Foo}>. That column will
then load a view-only field which may improve page load speed.

=item *

In the self service interface, the "Search Articles" box in the menu bar previously
was displayed to users who had the global right "ShowArticle". This is now
controlled by a new configuration option C<$SelfServiceShowArticleSearch>. This new
option defaults to off, so if you currently allow self service users to use article search,
enable this option to keep the article search box available.

=item *

System-level saved searches can now be displayed on the RT at a glance page.
Previously some users saw errors like:

    Either you have no rights to view saved search system-SavedSearch-34
    or identifier is incorrect

If you are still seeing that error after updating to RT 5.0.1, edit the page, remove
the saved search, save, then add it back again. After saving again, it should appear
as expected.

=item *

The System Configuration editor (Admin > Tools > System Configuration > Edit)
now uses JSON rather than Perl syntax to represent arrays and hashes.  Be
sure to enter valid JSON if you wish to modify an array- or hash-valued
configuration setting.

=back

=head1 UPGRADING FROM 5.0.1 AND EARLIER

=over 4

=item *

Previously C<$OwnerEmail> was shown on the RT login page for users to
contact with RT issues, in addition to being the address used to send various
errors like email bounces. A new config option C<$RTSupportEmail> is now used
for the login page display, allowing admins to set C<$OwnerEmail> to a different
address if desired, and possibly not display an email address on the login page.

If you want to still display your C<$OwnerEmail> on the login page, just set
C<$RTSupportEmail> to the same value.

=item * "RT at a glance" is now a dashboard

"RT at a glance" previously could be customized and was stored as
a special configuration used just for the homepage.
It is now a dashboard just like other dashboards in RT.
With this update, you can now easily change your entire homepage
by selecting a different dashboard to be your default homepage.
After upgrading, RT at a glance should look the same as it did
previously, but there are various changes in how it is managed.

The previous global RT at a glance page is converted to a new System
dashboard called "Homepage". Individual users with a custom homepage
will see a new dashboard in "My Dashboards" called Homepage. These are
regular dashboards now, so the names can be changed if desired.

The gears icon on the homepage now links to a page that displays all
available dashboards and users can select their default homepage from
the list. To customize, users can create a new dashboard. The privacy
of dashboards can be set to an individual user, a group, or system-wide,
depending on the user's rights. This makes it easy to set up and share
useful homepage configurations.

Users who want to customize their homepage need the rights "ModifySelf",
"CreateOwnDashboard", "DeleteOwnDashboard", "ModifyOwnDashboard" and
"SeeOwnDashboard". All users who have "ModifySelf" are automatically granted
these dashboard rights as part of the upgrade. You can modify these rights
as desired if you don't want users to be able to create dashboards.

All users can see the default System dashboard set for RT. If you
want to allow users to see other System dashboards, grant the
"SeeDashboard" right. This is not done automatically with the upgrade.

For RT admins, Admin > Global > RT at a glance is still available,
but instead of loading the page configuration editor, it shows a
list of System dashboards that can be set as the default homepage.
The RT at a glance option in the user admin page sub-menu also now shows
a list of dashboards to set for that user.

=back

=head1 UPGRADING FROM 5.0.0 AND 5.0.1

This section duplicates upgrading notes for changes included in
RT 4.4.5 and RT 5.0.2. These changes are duplicated here for
users upgrading from RT 5.0.0 or 5.0.1 who won't run the RT 4.4.5
upgrade.

=over 4

=item * Privacy Menu in Query Builder

On the Query Builder, the Privacy menu loads groups you are a member of as potential
places to save searches. However, it previously did not confirm the current user
had the EditSavedSearches right, so you might try to save a search with a group
and receive an error until that right was granted.

This has been fixed, so now groups load only if you have rights to create the
search via EditSavedSearches on the group or globally. This may change the groups
that appear in the Privacy menu, but shouldn't change functionality since users
without the correct rights were unable to create searches.

=item * AttachmentListCount Default

The C<AttachmentListCount> configuration option now defaults to 5.
To restore the previous configuration and show all attachments,
add the following to your C<RT_SiteConfig.pm>.

    Set($AttachmentListCount, undef);

=item * User Timezone and Dates in Ticket Searches

This releases fixes an issue with how "=" in time comparisons in ticket
searches applied timezone settings. Previously, dates would be adjusted
based on the global RT timezone even if the user had a different timezone.
This has been fixed to correctly use the user's timezone.

Note that this change may modify results for some saved searches for users
with a different timezone than RT's global setting.

=item * Script to reduce records in CachedGroupMembers

When adding groups to roles on tickets, we have found that caching the
members of these added groups in the CachedGroupMembers table makes
performance worse rather than improving it. This release includes updates
to no longer add these members recursively.

If you use groups in ticket roles, it's likely your CachedGroupMembers table
has a large number of now unnecessary records and these can hurt performance.
To delete these extra records run the following script:

    /opt/rt6/etc/upgrade/shrink-cgm-table

Depending on how many records your system has, this may take a while to run.
After you run this, you may have significantly reduced the number of records
in your CachedGroupMembers table, and may need to tell your database to
refresh indexes/statistics.

=item * Run Transaction Batch last, even in nested updates

When RT processes scrips, Batch mode scrips should always run last.
Previously, with nested updates, inner updates would run batch before
all outer updates were complete. One example of this is processing ticket
updates, the Basics update calls an inner "atomic" transaction to update
Owner, which would cause the unexpected batch run. This has been fixed
so batch runs only once for the outermost updates. All transactions
performed for that batch are available from the C<TransactionBatch> method
as expected.

=item * Ambiguous Owner order by option in search replaced with Owner.Name

RT 4.4.5 adds a bunch of new order by and format options for users and roles
to the Query Builder. For example, you can order by user fields on a user
like Owner.EmailAddress, Owner.RealName, or even Owner.Organization.
As part of this change, the previous Owner entry has been renamed to
Owner.Name.

The upgrade scripts include a step to make this change in any saved searches
in the database automatically. If you have Owner as an order by field in
searches stored elsewhere or as a link, you can update to Owner.Name manually.

=item * Default "order by" field for roles in search results

Because of the new options mentioned above, when displaying role information
we also set defaults for order by behavior when you click headers on search
results to re-sort them. For example, in a list of ticket results, you can
click on Requestors to re-sort the results by that field.

Previously this order by used EmailAddress. It now defaults to Name
because we believe that is more common for sorting, but because of
the new features you can change this in your search Format.
For example, you can update the line in the Format section on
the Advanced page to look like this:

    '<small>__Requestor.EmailAddress__</small>',

That column will then specifically show EmailAddress and when you click
it will order by EmailAddress.

=back

=head1 UPGRADING FROM 5.0.2 AND EARLIER

=over 4

=item * Fix for Mason cache handling

RT 5.0.2 introduced a new button on the System Configuration page to easily
clear the mason cache, and a bug was found related to the updated
Mason cache handling. The bug is most evident in extensions like
RTIR where some links will stop working correctly. This is because
some callbacks would not get correctly re-initialized on fresh page
loads. This bug is fixed in this release.

=item * Additional use of bind variables in queries

RT previously used bind variables in most queries, but some classes of queries,
like ad-hoc queries generated by the query builder, did not. This could cause
performance problems with Oracle, especially systems with very large databases.

RT 5.0.3, along with DBIx::SearchBuilder version 1.70 and newer, uses bind
variables for all queries. This should improve performance on Oracle and it may
help other databases also. If you were previously using cursor_sharing = FORCE
for your RT sessions in Oracle to help cache queries without bind parameters,
you can try switching to EXACT and testing performance after upgrading.

=back

=head1 UPGRADING FROM 5.0.3 AND EARLIER

=over 4

=item * Updated defaults for C<$WebSecureCookies>

The previous default value for the configuration option C<$WebSecureCookies>
was '0', meaning that RT did not, by default, set the C<Secure> option on
session cookies. The default for this option has been changed to '1', which
will require all users to connect to the RT instance over SSL and will trigger
other changes in browser behavior, such as cookie caching.

If you are running RT over http without SSL, this will cause problems and
you can set your local value back to '0'.

RT previously did not set a C<SameSite> policy for session cookies.  How this
is handled by browsers varies.  RT 5.0.4 introduces the configuration option
C<$WebSameSiteCookies> with a default value of 'Lax', which provides
additional defense against CSRF attacks in some browsers.  See
L<https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie/SameSite>
for more details on valid values, their meaning, and browser support.

=item * Removed dependency on Pod::Select

We no longer depend on the Pod::Select Perl module since it has been deprecated
following its removal from the Perl core.

=item * Perl module change to GraphViz2

RT 4.4.6 and earlier use the Perl GraphViz module for interfacing with the graphviz
library for generating ticket link graphs.  That module has been deprecated so
we have replaced it with the GraphViz2 module.

Systems using C<--enable-graphviz> will be prompted to install the Perl
GraphViz2 module when upgrading.

=item * New C<$EmailDashboardInlineCSS> option for dashboard email

RT's email dashboard feature tries to send an HTML email that looks as much
like the RT dashboard as possible. In doing so, it pulls in a large amount
of CSS, creating very large emails. Not all of that CSS is needed, so
we have added the new option C<$EmailDashboardInlineCSS> to inline the
CSS. We have found this reduces the size of the dashboard emails
significantly and can help with rendering in some email clients.

To use this new feature, you must install the optional Perl module
L<CSS::Inliner>, version 4018 or later, then enable the feature in
your RT configuration.

=item * ModifyLoginRedirect callback in Logout.html moved

We try hard not to modify callbacks since they are made for external
code to reference, but in this case the logic of the page changed
and we had to move the callback location so it could correctly
modify the URL value, if needed. If you were using this callback to
modify the redirect URL on logout, your code will continue to work
as intended. However, if you were using this callback for other
reasons, you may need to update your code to use the C<BeforeSessionDelete>
callback instead.

=item * Custom role keys in REST2 ticket endpoints changed

We updated custom role keys from "GroupType" syntax like "RT::CustomRole-1"
to "Name" in REST2 ticket endpoints, to be consistent with core roles.
We also added a "CustomRoles" entry to cover all custom roles, making it
consistent with similar results for "CustomFields".

For example, the GET response of C<XX_RT_URL_XX/REST/2.0/ticket/ID> changes
from this:

    {
        ...
        "RT::CustomRole-1" : [
           {
              "id" : "root",
              "type" : "user",
              "_url" : "XX_RT_URL_XX/REST/2.0/user/root"
           }
        ],
        ...
    }

to:

    {
        ...
        "Manager" : [
           {
              "id" : "root",
              "type" : "user",
              "_url" : "XX_RT_URL_XX/REST/2.0/user/root"
           }
        ],
        "CustomRoles" : {
           "Manager" : [
              {
                 "id" : "root",
                 "type" : "user",
                 "_url" : "XX_RT_URL_XX/REST/2.0/user/root"
              }
           ]
        },
        ...
    }

We recommend using the "CustomRoles" section because individual top
level custom role entries like the "Manager" following "..." in
the above example will be removed in the future.

=item * DBD::SQLite Dependency updated to 1.72

We use the wonderful L<SQLite|https://www.sqlite.org> database for
testing, although we don't recommend it for production RT installations.
Updates in RT 5.0.4 require a new version of L<DBD::SQLite> and this will
be checked during the normal C<make testdeps> step on upgrade if it is
used based on your configuration. We do not test upgrades on SQLite
databases, so if you are using SQLite in some way
with your RT, make sure to take backups before upgrading.

=item * New search URL shortener

RT will now shorten search URLs by default, so instead of the longer
URLs previously seen when using the Query Builder, you will now see a short
code in the browser URL bar. This update makes sharing searches much easier
and resolves some issues with extremely long search URLs. Any existing search
URLs saved as bookmarks should continue to work as normal.

This new feature requires a new table, which is installed automatically
as part of the upgrade process. If you prefer not to use shortened URLs,
you can disable this new feature by setting C<$EnableURLShortener> to
false.

=item * HTML Custom Fields

RT now supports an C<HTML> type for custom fields, so if you have custom
fields containing C<HTML>, you can update them and switch the type to C<HTML>
to use CKEditor for editing. This is specifically useful for the Content
custom field in articles.

=item * MySQL 8 now supported

Starting with RT 5.0.4, RT now supports MySQL 8. Note that as part of this upgrade
you also need to update the module L<DBIx::SearchBuilder>.

=back

=head1 UPGRADING FROM 5.0.4 AND EARLIER

=over 4

=item Update Messages Changed for Consistency

Some parts of RT, notably Bulk Update, previously could show update messages
like:

    Ticket 123: Ticket 123: Status changed from 'new' to 'open'

This is fixed in RT 5.0.5. As part of this fix, some JSON responses sent for
REST 2 operations are also updated. For example, an Article update message
is changed:

    Old: Article More updates using REST: Name changed from...
    New: Article 123: Name changed from...

If you have any automation using REST 2 that checks these JSON response
messages, you may need to update your system to match the new format.

=back

=head1 UPGRADING FROM 5.0.5 AND EARLIER

=over 4

=item Ticket Owner Updates and Notifications

When processing ticket updates, RT previously processed the reply/comment
before processing other ticket updates, including owner changes. For RTs
configured to send email to some users only when they are the ticket owner,
this processing order resulted in new owners not seeing the reply/comment associated
with the update that made them the new owner. This could cause confusion, especially
if the reply/comment included information specifically addressed to the new
owner.

To fix this issue, owner changes are now processed before messages, so new
owners will now see the message associated with the change that made them
owner.

This will result in new email being sent when it wasn't previously. We believe
this fixes the previous incorrect behavior. However, if you relied on this behavior,
and don't want the new email, you may need to modify your scrip configurations.

=item Spreadsheet (TSV) Download Format

The format of some column headers in spreadsheets (TSV files) downloaded from ticket
search results has been updated. Specifically custom fields and custom roles no
longer show "CustomField.{}" or "CustomRole.{}" in the header. Also, multi-word
headers like "EmailAddress" now have spaces added so the header will appear like
"Email Address".

This should make headers more readable, but if you have any automated processes that
parse the headers, you will need to update your parsing code.

=item Running RT with MariaDB and MySQL 5.7

RT uses the perl module DBD::mysql to connect to MySQL-type databases, and before
version 5.001, it worked with older MySQL versions like 5.7, newer versions like 8,
and all versions of MariaDB. Starting with DBD::mysql 5.001, it supports only
MySQL 8 and newer.

To align with this change, RT's C<configure> script now has two new options available
for C<--with-db-type>. To run with MySQL 5.7 or older, use C<mysql5>. To run with
MariaDB, use C<MariaDB>. These will configure the installer to use an older,
compatible version of DBD::mysql.

If you install a newer version of DBD::mysql by mistake, you can uninstall it or
manually force install a version older than 5.001.

=item Unlimited Option in SearchResultsPerPage Configuration

RT 5.0.4 added C<@SearchResultsPerPage> as a configuration option to allow admins to
control the options presented in the "Rows per page" dropdown in the Query Builder.
When it was added, the "Unlimited" option was automatically added to the list of options
configured. This prevented admins from removing the "Unlimited" option from the
list, so this has been updated in RT 5.0.6 to use the configured options only with
no other options added automatically.

If you previously set a custom C<@SearchResultsPerPage> and you want to keep the
"Unlimited" option, update your configuration and add "0" to your list.

=back

=head1 UPGRADING FROM 5.0.7 AND EARLIER

=over 4

=item Enabling Scheduled Processes in the Web UI

RT 5.0.8 adds a new page for administrators to schedule automated processes
in the web UI. This allows SuperUsers to add and modify C<rt-crontool> jobs
that previously had to be managed on the server directly in C<cron>.

To enable this, schedule the new utility C<bin/rt-run-scheduled-processes> in
cron to run every 15 minutes. This job will then run any jobs scheduled in the
web UI.

=back

=head1 UPGRADING FROM 5.0.8 AND EARLIER

=over 4

=item Helpers/Autocomplete/Articles ModifySuggestion Callback Updated

The autocomplete helper endpoint at Helpers/Autocomplete/Articles has a
callback ModifySuggestion. This callback mirrors similar callbacks in the
Users and Groups endpoints. However, when it was added, the pattern in
Users and Groups was not copied correctly and the callback passed the
full array, even though it is called for each article, and it used a
parameter "label" instead of "article" for the article object. This
is now fixed and the ModifySuggestion callback in Articles follows the
same pattern as Users and Groups.

Given the strange arguments in the previous callback, we think it's unlikely
it is being used. However, if you were using this callback, you will need
to update your code for the new parameters.

=item Log level of RT::Action::SetStatus unresolved messages

When calling RT::Action::SetStatus via rt-crontool, the operation will fail
if the ticket has unresolved dependencies (linked tickets). This failure is
logged and previously it used the "error" level. Since this is an informational
message and not a system error, we have changed the log level for these
"unresolved" messages to warning. All other failures are still error.

This makes it possible for admins to better tune error notifications
and alert on errors, but not warnings based on linked tickets.

=back

=head1 UPGRADING FROM 5.0.9 AND EARLIER

=over 4

=item Support to allow links from Android Apps

Links to RT from Android apps like Slack send a Referer header in the form
C<android-app://com.slack/> and previously this generated an error because RT
expected schemes that represented a host, like http[s]. The C<ReferrerWhitelist>
configuration option now accepts scheme as part of the configuration so you can
whitelist Android apps now, e.g.

    Set(@ReferrerWhitelist, qw(android-app://com.slack/));

=back

=cut
