Add cache_action to repository compare

config/feature_flags/development/api_caching_rate_limit_repository_compare.yml

+---
+name: api_caching_rate_limit_repository_compare
+introduced_by_url: 
+rollout_issue_url: 
+milestone: '14.0'
+type: development
+group: group::source code
+default_enabled: false

lib/api/repositories.rb

@@ -120,6 +120,9 @@ module API
         optional :straight, type: Boolean, desc: 'Comparison method, `true` for direct comparison between `from` and `to` (`from`..`to`), `false` to compare using merge base (`from`...`to`)', default: false
       end
       get ':id/repository/compare' do
+        ff_enabled = Feature.enabled?(:api_caching_rate_limit_repository_compare, user_project, default_enabled: :yaml)
+
+        cache_action_if(ff_enabled, [user_project, :repository_compare, current_user, declared_params], expires_in: 30.seconds) do
           if params[:from_project_id].present?
             target_project = MergeRequestTargetProjectFinder
               .new(current_user: current_user, source_project: user_project, project_feature: :repository)
@@ -140,6 +143,7 @@ module API
             not_found!("Ref")
           end
         end
+      end
 
       desc 'Get repository contributors' do
         success Entities::Contributor