feat: add note about new OCP \OCP\Search\IExternalProvider interface

Signed-off-by: Andrey Borysenko <andrey18106x@gmail.com>

developer_manual/app_publishing_maintenance/app_upgrade_guide/upgrade_to_32.rst

@@ -51,6 +51,7 @@ Added APIs
 - New method ``\OCP\Files\Template\BeforeGetTemplatesEvent::shouldGetFields`` to get the event's ``withFields`` property, which should determine whether or not to perform template field extraction on the returned templates.
 - New interface ``\OCP\OCM\ICapabilityAwareOCMProvider`` to extend the OCM provider with 1.1 and 1.2 extensions of the Open Cloud Mesh Discovery API
 - New task processing task type ``OCP\TaskProcessing\AnalyzeImages`` to ask questions about images.
+- New interface ``\OCP\Search\IExternalProvider`` allows extending the search provider with an explicit flag to indicate that the search is performed on external (3rd-party) resources. This is used in Unified Search to disable searches through these by default (via a toggle switch).
 
 Changed APIs
 ^^^^^^^^^^^^

developer_manual/digging_deeper/search.rst

@@ -228,6 +228,13 @@ This interface allows to supports other filtering types.
 
 ``getCustomFilters`` allows to declare specific filters. In current state, the specific filters will only be available in the API.
 
+External search provider
+------------------------
+
+Since Nextcloud 32, to improve privacy, you can extend your provider with the ``\OCP\Search\IExternalProvider`` interface and implement the ``isExternalProvider()`` method to indicate that the search is performed on external (3rd-party) resources.
+In the Unified Search UI, searching through these providers is disabled by default (via toggle switch).
+
+
 Provider registration
 ---------------------