Update commented_by implementation

Next iteration of adding `commented_by` to the API. This
commit relocates where it's implemented, preparing to
fetch the real data.

ee/app/models/approval_wrapped_rule.rb

@@ -74,6 +74,12 @@ class ApprovalWrappedRule
     end
   end
 
+  def commented_approvers
+    strong_memoize(:commented_approvers) do
+      []
+    end
+  end
+
   def approved?
     strong_memoize(:approved) do
       approvals_left <= 0 || unactioned_approvers.size <= 0

ee/lib/ee/api/entities/merge_request_approval_setting_rule.rb

@@ -9,6 +9,7 @@ module EE
       # To be removed in https://gitlab.com/gitlab-org/gitlab/issues/13574.
       class MergeRequestApprovalSettingRule < MergeRequestApprovalStateRule
         expose :approvers, using: ::API::Entities::UserBasic, override: true
+        expose :commented_approvers, as: :commented_by, using: ::API::Entities::UserBasic
       end
     end
   end

ee/lib/ee/api/entities/merge_request_approval_state_rule.rb

@@ -7,8 +7,6 @@ module EE
         expose :code_owner
         expose :approved_approvers, as: :approved_by, using: ::API::Entities::UserBasic
         expose :approved?, as: :approved
-
-        expose :approved_approvers, as: :commented_by, using: ::API::Entities::UserBasic
       end
     end
   end

ee/spec/models/approval_wrapped_rule_spec.rb

@@ -138,6 +138,12 @@ RSpec.describe ApprovalWrappedRule do
     end
   end
 
+  describe "#commented_approvers" do
+    it "returns an array" do
+      expect(subject.commented_approvers).to be_an(Array)
+    end
+  end
+
   describe '#unactioned_approvers' do
     context 'when some approvers has not approved yet' do
       before do

ee/spec/requests/api/merge_request_approvals_spec.rb

@@ -174,7 +174,7 @@ RSpec.describe API::MergeRequestApprovals do
       expect(rule_response['name']).to eq('foo')
       expect(rule_response['approvers'][0]['username']).to eq(approver.username)
       expect(rule_response['approved_by'][0]['username']).to eq(approver.username)
-      expect(rule_response['commented_by'][0]['username']).to eq(approver.username)
+      expect(rule_response['commented_by']).to eq([])
       expect(rule_response['source_rule']).to be_nil
       expect(rule_response['section']).to be_nil
     end