Continue from https://gitlab.com/gitlab-org/gitlab/-/issues/571916. Break down https://gitlab.com/gitlab-org/gitlab-development-kit/-/merge_requests/5555 into reviewable, mergeable slices. For example add sufficient unit tests. The result should be a GDK CI job that runs this test and succeeds only if org migration (replication for now, if cutover is not working yet) succeeds.