🎉 Add media-object lifecycle handling.

backend/resources/migrations/0018-add-file-trimming-triggers.sql

@@ -0,0 +1,25 @@
+ALTER TABLE file
+  ADD COLUMN has_media_trimmed boolean DEFAULT false;
+
+CREATE INDEX file__modified_at__has_media_trimed__idx
+    ON file(modified_at)
+ WHERE has_media_trimmed IS false;
+
+CREATE FUNCTION on_media_object_insert()
+  RETURNS TRIGGER AS $$
+  BEGIN
+    UPDATE file
+       SET has_media_trimmed = false,
+           modified_at = now()
+     WHERE id = NEW.file_id;
+    RETURN NEW;
+  END;
+$$ LANGUAGE plpgsql;
+
+CREATE TRIGGER media_object__insert__tgr
+AFTER INSERT ON media_object
+   FOR EACH ROW EXECUTE PROCEDURE on_media_object_insert();
+
+CREATE TRIGGER media_thumbnail__on_delete__tgr
+ AFTER DELETE ON media_thumbnail
+   FOR EACH ROW EXECUTE PROCEDURE handle_delete();