Send :use_specialized_service param for MRs

This ensures the new service is called when the add_spent_time endpoint
for merge requests is used.

The update service for issues does not know anything about this parameter
so we skip it when the object to add spent time to is an issue.

lib/api/time_tracking_endpoints.rb

@@ -85,10 +85,15 @@ module API
       post ":id/#{issuable_collection_name}/:#{issuable_key}/add_spent_time" do
         authorize! admin_issuable_key, load_issuable
 
-        update_issuable(spend_time: {
-          duration: Gitlab::TimeTrackingFormatter.parse(params.delete(:duration)),
-          user_id: current_user.id
-        })
+        update_params = {
+          spend_time: {
+            duration: Gitlab::TimeTrackingFormatter.parse(params.delete(:duration)),
+            user_id: current_user.id
+          }
+        }
+        update_params[:use_specialized_service] = true if issuable_name == 'merge_request'
+
+        update_issuable(update_params)
       end
 
       desc "Reset spent time for a project #{issuable_name}"

spec/support/shared_examples/requests/api/time_tracking_shared_examples.rb

@@ -125,6 +125,22 @@ RSpec.shared_examples 'time tracking endpoints' do |issuable_name|
         expect(json_response['message']['base'].first).to eq(_('Time to subtract exceeds the total time spent'))
       end
     end
+
+    if issuable_name == 'merge_request'
+      it 'calls update service with :use_specialized_service param' do
+        expect(::MergeRequests::UpdateService).to receive(:new).with(project, user, hash_including(use_specialized_service: true))
+
+        post api("/projects/#{project.id}/#{issuable_collection_name}/#{issuable.iid}/add_spent_time", user), params: { duration: '2h' }
+      end
+    end
+
+    if issuable_name == 'issue'
+      it 'calls update service without :use_specialized_service param' do
+        expect(::Issues::UpdateService).to receive(:new).with(project, user, hash_not_including(use_specialized_service: true))
+
+        post api("/projects/#{project.id}/#{issuable_collection_name}/#{issuable.iid}/add_spent_time", user), params: { duration: '2h' }
+      end
+    end
   end
 
   describe "POST /projects/:id/#{issuable_collection_name}/:#{issuable_name}_id/reset_spent_time" do