Allow auditor to view grop productivity analytics

The auditor role should be able to view productivity analytics
of a group they are not a member of, as per our docs.

Changelog: fixed
EE: true

ee/app/policies/ee/group_policy.rb

@@ -171,6 +171,10 @@ module EE
         enable :admin_protected_environment
       end
 
+      rule { auditor }.policy do
+        enable :view_productivity_analytics
+      end
+
       rule { owner | admin }.policy do
         enable :owner_access
       end

ee/spec/controllers/groups/analytics/productivity_analytics_controller_spec.rb

@@ -74,6 +74,16 @@ RSpec.describe Groups::Analytics::ProductivityAnalyticsController do
         let(:target_id) { 'g_analytics_productivity' }
       end
     end
+
+    context 'when user is an auditor' do
+      let(:current_user) { create(:user, :auditor) }
+
+      it 'allows access' do
+        subject
+
+        expect(response).to have_gitlab_http_status(:success)
+      end
+    end
   end
 
   describe 'GET show.json' do