Finalize data migration, add FK on `Project#creator_id`
Based on the comment at !110485 (comment 1260700325):
The steps should be:
- Make sure there are no longer any invalid data on gitlab.com database using
database-lab
- Finalize the data migration in !110485 (merged)
- Add a NOT VALID foreign key constraint to the column to ensure GitLab doesn’t create inconsistent records.
Edited by Manoj M J