* requiring md5 and size of artifacts so that we can report them in artifact REST API

manifest

@@ -53,4 +53,5 @@ invited_users.sql
 collapse_user_and_admin.sql
 default_gender_to_null.sql
 subscribe_email.sql
-notifications.sql
+notifications.sql
+artifact_metadata.sql

up/artifact_metadata.sql

@@ -0,0 +1,3 @@
+-- add a size field and make md5 required
+ALTER TABLE artifact_updates ADD COLUMN size INTEGER NOT NULL;
+ALTER TABLE artifact_updates ALTER COLUMN sha1 SET NOT NULL;