This is a mess... Using prepend will give a different ancestors
chain we're not expecting. To fix this we'll need to know what
exactly methods we want to use in each classes using this module.
1. Previously, we were not removing existing access levels before
creating new ones. This is not a problem for EE, but _is_ for CE,
since we restrict the number of access levels in CE to 1.
2. The correct approach is:
CE -> delete all access levels before updating a protected branch
EE -> delete developer access levels if "developers_can_{merge,push}" is switched off
3. The dispatch is performed by checking if a "length: 1" validation is
present on the access levels or not.
4. Another source of problems was that we didn't put multiple queries in
a transaction. If the `destroy_all` passes, but the `update` fails,
we should have a rollback.
5. Modifying the API to provide users direct access to CRUD access
levels will make things a lot simpler.
6. Create `create/update` services separately for this API, which
perform the necessary data translation, before calling the regular
`create/update` services. The translation code was getting too large
for the API endpoint itself, so this move makes sense.
!581 has a lot of changes that would cause merge conflicts if not
properly backported to CE. This commit/MR serves as a better
foundation for gitlab-org/gitlab-ee!581.
= Changes =
1. Move from `has_one {merge,push}_access_level` to `has_many`, with the
`length` of the association limited to `1`. This is _effectively_ a
`has_one` association, but should cause less conflicts with EE, which
is set to `has_many`. This has a number of related changes in the
views, specs, and factories.
2. Make `gon` variable loading more consistent (with EE!581) in the
`ProtectedBranchesController`. Also use `::` to prefix the
`ProtectedBranches` services, because this is required in EE.
3. Extract a `ProtectedBranchAccess` concern from the two access level
models. This concern only has a single `humanize` method here, but
will have more methods in EE.
4. Add `form_errors` to the protected branches creation form. This is
not strictly required for EE compatibility, but was an oversight
nonetheless.
