Add `approved_by_users` relation to merge_requests

This could be a relation that is easily preloaded.

ee/app/controllers/ee/projects/merge_requests_controller.rb

@@ -41,10 +41,12 @@ module EE
         return super unless APPROVAL_RENDERING_ACTIONS.include?(action_name.to_sym)
 
         @issuable = @merge_request ||= project.merge_requests
-                                         .includes(approvals: :user,
-                                                   approvers: :user,
-                                                   approver_groups: :group)
+                                         .includes(
+                                           :approved_by_users,
+                                           approvers: :user
+                                         )
                                          .find_by!(iid: params[:id])
+        super
       end
       # rubocop:disable Gitlab/ModuleWithInstanceVariables
 

ee/app/models/concerns/approvable.rb

@@ -79,7 +79,7 @@ module Approvable
     approvers_relation = approvers_overwritten? ? approvers : target_project.approvers
     approvers_relation = approvers_relation.where.not(user_id: author.id) if author
 
-    approvers_relation
+    approvers_relation.includes(:user)
   end
 
   def overall_approver_groups
@@ -144,10 +144,6 @@ module Approvable
     remaining_approvals.zero? || remaining_approvals > approvers_left.count
   end
 
-  def approved_by_users
-    approvals.map(&:user)
-  end
-
   def approver_ids=(value)
     value.split(",").map(&:strip).each do |user_id|
       next if author && user_id == author.id

ee/app/models/ee/merge_request.rb

@@ -6,6 +6,7 @@ module EE
 
     included do
       has_many :approvals, dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
+      has_many :approved_by_users, through: :approvals, source: :user
       has_many :approvers, as: :target, dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
       has_many :approver_groups, as: :target, dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
 

ee/spec/models/merge_request_spec.rb

@@ -11,6 +11,7 @@ describe MergeRequest do
     it { is_expected.to have_many(:approvals).dependent(:delete_all) }
     it { is_expected.to have_many(:approvers).dependent(:delete_all) }
     it { is_expected.to have_many(:approver_groups).dependent(:delete_all) }
+    it { is_expected.to have_many(:approved_by_users) }
   end
 
   describe '#squash_in_progress?' do

spec/lib/gitlab/import_export/all_models.yml

@@ -95,6 +95,7 @@ merge_requests:
 - timelogs
 - head_pipeline
 - latest_merge_request_diff
+- approved_by_users
 merge_request_diff:
 - merge_request
 - merge_request_diff_commits