Backport API changes needed to fix sticking in EE
This backports some changes from https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1502 where the code is shared with CE, reducing the number of merge conflicts.
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
This backports some changes from https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1502 where the code is shared with CE, reducing the number of merge conflicts.