Add link to "Gitlab external user creator" repo.
Creating a merge request as advised by @kelvinmutuma, https://forum.gitlab.com/t/gitlab-external-users-and-user-creator/2595.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Creating a merge request as advised by @kelvinmutuma, https://forum.gitlab.com/t/gitlab-external-users-and-user-creator/2595.