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, 10 insertions, 3 deletions

diff --git a/app/services/git_push_service.rb b/app/services/git_push_service.rb
index 604737e6934..3f6a177bf3a 100644
--- a/app/services/git_push_service.rb
+++ b/app/services/git_push_service.rb
@@ -88,10 +88,17 @@ class GitPushService < BaseService
 
     # Set protection on the default branch if configured
     if current_application_settings.default_branch_protection != PROTECTION_NONE
-      allowed_to_push = current_application_settings.default_branch_protection == PROTECTION_DEV_CAN_PUSH ? 'developers' : 'masters'
-      allowed_to_merge = current_application_settings.default_branch_protection == PROTECTION_DEV_CAN_MERGE ? 'developers' : 'masters'
 
-      params = { name: @project.default_branch, allowed_to_push: allowed_to_push, allowed_to_merge: allowed_to_merge }
+      params = {
+        name: @project.default_branch,
+        push_access_level_attributes: {
+          access_level: current_application_settings.default_branch_protection == PROTECTION_DEV_CAN_PUSH ? Gitlab::Access::DEVELOPER : Gitlab::Access::MASTER
+        },
+        merge_access_level_attributes: {
+          access_level: current_application_settings.default_branch_protection == PROTECTION_DEV_CAN_MERGE ? Gitlab::Access::DEVELOPER : Gitlab::Access::MASTER
+        }
+      }
+
       ProtectedBranches::CreateService.new(@project, current_user, params).execute
     end
   end