Send root_namespace_id to the Projects::ProjectDeletedEvent

To be able to invalidate the GitLab Pages internal API cache when a
Project is deleted, this event now also provides the deleted project's
`root_namespace_id`.

Related to: #364065

Changelog: changed

app/events/projects/project_deleted_event.rb

@@ -7,7 +7,8 @@ def schema
         'type' => 'object',
         'properties' => {
           'project_id' => { 'type' => 'integer' },
-          'namespace_id' => { 'type' => 'integer' }
+          'namespace_id' => { 'type' => 'integer' },
+          'root_namespace_id' => { 'type' => 'integer' }
         },
         'required' => %w[project_id namespace_id]
       }

app/services/projects/destroy_service.rb

@@ -263,8 +263,12 @@ def flush_caches(project)
     end
 
     def publish_project_deleted_event_for(project)
-      data = { project_id: project.id, namespace_id: project.namespace_id }
-      event = Projects::ProjectDeletedEvent.new(data: data)
+      event = Projects::ProjectDeletedEvent.new(data: {
+        project_id: project.id,
+        namespace_id: project.namespace_id,
+        root_namespace_id: project.root_namespace.id
+      })
+
       Gitlab::EventStore.publish(event)
     end
   end

spec/events/projects/project_deleted_event_spec.rb

@@ -6,6 +6,7 @@
   where(:data, :valid) do
     [
       [{ project_id: 1, namespace_id: 2 }, true],
+      [{ project_id: 1, namespace_id: 2, root_namespace_id: 3 }, true],
       [{ project_id: 1 }, false],
       [{ namespace_id: 1 }, false],
       [{ project_id: 'foo', namespace_id: 2 }, false],

spec/services/projects/destroy_service_spec.rb

@@ -26,7 +26,11 @@
     end
 
     it 'publishes a ProjectDeleted event with project id and namespace id' do
-      expected_data = { project_id: project.id, namespace_id: project.namespace_id }
+      expected_data = {
+        project_id: project.id,
+        namespace_id: project.namespace_id,
+        root_namespace_id: project.root_namespace.id
+      }
 
       expect { destroy_project(project, user, {}) }.to publish_event(Projects::ProjectDeletedEvent).with(expected_data)
     end