PR: https://github.com/go-gitea/gitea/pull/18461
Use created_at instead of updated_at because it makes more sense.
Fallback to updated_at if it is missing and to time.Now() if it is
also missing.
Fixes: #18434
Co-authored-by: Loïc Dachary <loic@dachary.org>
Conflicts:
services/migrations/gitlab.go
trivial context conflict because var reviews became reviews := in 1.17