feat: Video editor supports transcripts [FC-0076] (#36058)

* Add error handler on save video to avoid creating sjson
* Support transcripts without edx_video_id in definition_to_xml
* When copying a video from a library to a course: Create a new edx_video_id
* Save transcripts as static assets in a video in a library when adding a new transcript.
* Delete transcripts as static assets in a video in a library when deleting transcripts.
* Support download transcript in a video in a library.
* Support replace transcript in a video in a library.
* Support updating transcripts in video in a library.
* Refactor the code of downloading YouTube transcripts to enable this feature in libraries.
* Support copy from a library to a course and a course to a library.

cms/djangoapps/contentstore/rest_api/v2/views/downstreams.py

@@ -88,6 +88,7 @@ from openedx.core.lib.api.view_utils import (
     DeveloperErrorViewMixin,
     view_auth_classes,
 )
+from xmodule.video_block.transcripts_utils import clear_transcripts
 from xmodule.modulestore.django import modulestore
 from xmodule.modulestore.exceptions import ItemNotFoundError
 
@@ -224,6 +225,9 @@ class SyncFromUpstreamView(DeveloperErrorViewMixin, APIView):
         """
         downstream = _load_accessible_block(request.user, usage_key_string, require_write_access=True)
         try:
+            if downstream.usage_key.block_type == "video":
+                # Delete all transcripts so we can copy new ones from upstream
+                clear_transcripts(downstream)
             upstream = sync_from_upstream(downstream, request.user)
             static_file_notices = import_static_assets_for_library_sync(downstream, upstream, request)
         except UpstreamLinkException as exc:

cms/djangoapps/contentstore/rest_api/v2/views/tests/test_downstreams.py

@@ -264,7 +264,8 @@ class PostDownstreamSyncViewTest(_DownstreamSyncViewTestMixin, SharedModuleStore
     @patch.object(UpstreamLink, "get_for_block", _get_upstream_link_good_and_syncable)
     @patch.object(downstreams_views, "sync_from_upstream")
     @patch.object(downstreams_views, "import_static_assets_for_library_sync", return_value=StaticFileNotices())
-    def test_200(self, mock_sync_from_upstream, mock_import_staged_content):
+    @patch.object(downstreams_views, "clear_transcripts")
+    def test_200(self, mock_sync_from_upstream, mock_import_staged_content, mock_clear_transcripts):
         """
         Does the happy path work?
         """
@@ -273,6 +274,7 @@ class PostDownstreamSyncViewTest(_DownstreamSyncViewTestMixin, SharedModuleStore
         assert response.status_code == 200
         assert mock_sync_from_upstream.call_count == 1
         assert mock_import_staged_content.call_count == 1
+        assert mock_clear_transcripts.call_count == 1
 
 
 class DeleteDownstreamSyncViewtest(_DownstreamSyncViewTestMixin, SharedModuleStoreTestCase):