Merge pull request #13066 from nextcloud/backport/13063/stable31

[stable31] feat: Document new query parameter forceLanguage

developer_manual/app_publishing_maintenance/app_upgrade_guide/upgrade_to_31.rst

@@ -125,6 +125,7 @@ Added APIs
 - New events ``OCP\User\Events\BeforeUserIdUnassignedEvent``, ``OCP\User\Events\UserIdUnassignedEvent``, and ``OCP\User\Events\UserIdAssignedEvent`` have been added to replace the hooks ``\OC\User::preUnassignedUserId``, ``\OC\User::postUnassignedUserId`` and ``\OC\User::assignedUserId``.
 - New interface ``OCP\Files\Storage\IConstructableStorage`` for storages that can be built by passing only an array to the constructor.
 - New service ``OCP\RichObjectStrings\IRichTextFormatter`` to format rich text into parsed plain text using its ``richToParsed`` method.
+- New magic query parameter ``forceLanguage`` to force a specific language for a web request (API or frontend). See :ref:`Forcing language for a given call<api-force-language>`.
 
 Changed APIs
 ^^^^^^^^^^^^

developer_manual/client_apis/OCS/ocs-api-overview.rst

@@ -255,3 +255,14 @@ In case needed, you can also further filter the auto-complete results on the PHP
 ``OCP\Collaboration\AutoComplete\AutoCompleteEvent`` event. The event gives you access to the current
 result set, the item and share types and some more information that you can use to e.g. limit the autocomplete
 results to users that are actually in the current chat conversation.
+
+.. _api-force-language:
+
+Force language for a given call
+-------------------------------
+
+All Nextcloud API calls support forcing the language using the query parameter ``forceLanguage``. It will override any user setting for the given call.
+
+.. code-block:: bash
+
+    curl -u username:password -X GET 'https://cloud.example.com/ocs/v1.php/...?forceLanguage=en' -H "OCS-APIRequest: true"