TEST ONLY: Backfill `member_namespace_id` for `GroupMember`
requested to merge jcunha-349575-backfill-member_namespace_id-with-proper-data-either-the-group-id-or-the-project-cp into master
What does this MR do and why?
TO BE DELETED AFTER TESTED
This MR is simply to force the sync execution of the batched migration on the db testing job.