#mitra
I successfully completed the full migration to the proxy by running this command. (Of course, I did so at my own risk.)
UPDATE media_attachment SET media=jsonb_build_object( 'url', media->'url', 'type', 'link', 'media_type', media->'media_type' ) WHERE media->>'url' IS NOT NULL;
UPDATE emoji SET image=jsonb_build_object( 'url', image->'url', 'type', 'link', 'media_type', image->'media_type' ) WHERE image->>'url' IS NOT NULL;
