Use `Gitlab::Access` to protected branch access levels.

1. It makes sense to reuse these constants since we had them duplicated
   in the previous enum implementation. This also simplifies our
   `check_access` implementation, because we can use
   `project.team.max_member_access` directly.

2. Use `accepts_nested_attributes_for` to create push/merge access
   levels. This was a bit fiddly to set up, but this simplifies our code
   by quite a large amount. We can even get rid of
   `ProtectedBranches::BaseService`.

3. Move API handling back into the API (previously in
   `ProtectedBranches::BaseService#translate_api_params`.

4. The protected branch services now return a `ProtectedBranch` rather
   than `true/false`.

5. Run `load_protected_branches` on-demand in the `create` action, to
   prevent it being called unneccessarily.

6. "Masters" is pre-selected as the default option for "Allowed to Push"
   and "Allowed to Merge".

7. These changes were based on a review from @rymai in !5081.

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index e51bee5c846..4eb95d8a215 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -127,12 +127,12 @@ module API
 
       expose :developers_can_push do |repo_branch, options|
         project = options[:project]
-        project.protected_branches.matching(repo_branch.name).any? { |protected_branch| protected_branch.push_access_level.developers? }
+        project.protected_branches.matching(repo_branch.name).any? { |protected_branch| protected_branch.push_access_level.access_level == Gitlab::Access::DEVELOPER }
       end
 
       expose :developers_can_merge do |repo_branch, options|
         project = options[:project]
-        project.protected_branches.matching(repo_branch.name).any? { |protected_branch| protected_branch.merge_access_level.developers? }
+        project.protected_branches.matching(repo_branch.name).any? { |protected_branch| protected_branch.merge_access_level.access_level == Gitlab::Access::DEVELOPER }
       end
     end