Only allow MusicBrainz tagged file on a pod (#2083)

Part-of: <https://dev.funkwhale.audio/funkwhale/funkwhale/-/merge_requests/2607>

api/funkwhale_api/music/tasks.py

@@ -247,6 +247,15 @@ def process_upload(upload, update_denormalization=True):
             return fail_import(
                 upload, "invalid_metadata", detail=detail, file_metadata=metadata_dump
             )
+        if (
+            settings.ONLY_ALLOW_MUSICBRAINZ_TAGGED_FILES is True
+            and not serializer.validated_data.get("mbid")
+        ):
+            return fail_import(
+                upload,
+                "Uploading files without a MusicBrainz ID is not permitted in this pod",
+                detail="You can tag you files with MusicBrainz Picard",
+            )
 
         final_metadata = collections.ChainMap(
             additional_data, serializer.validated_data, internal_config