Merge pull request Sylius#9456 from pamil/1.2-custom-repo-docs

Add documentation for using custom repository service in ResourceBundle

docs/components_and_bundles/bundles/SyliusResourceBundle/show_resource.rst

@@ -87,6 +87,28 @@ Creating yet another action to change the method called could be a solution but
 
 Internally, it simply uses the ``$repository->findOneNewestByAuthor($author)`` method, where ``author`` is taken from the current request.
 
+Using Custom Repository Service
+-------------------------------
+
+If you would like to use your own service to get the resource, then try the following configuration:
+
+.. code-block:: yaml
+
+    # app/config/routing.yml
+
+    app_book_show:
+        path: /books/{author}
+        methods: [GET]
+        defaults:
+            _controller: app.controller.book:showAction
+            _sylius:
+                repository:
+                    method: ["expr:service('app.repository.custom_book_repository')", "findOneNewestByAuthor"]
+                    arguments: [$author]
+
+
+With this configuration, method ``findOneNewestByAuthor`` from service with ID ``app.repository.custom_book_repository`` will be called to get the resource.
+
 Configuration Reference
 -----------------------