The default Content Delivery API implementation and features can be found in different API endpoints. These controllers are using services, builders, etc. which are in a deeper a layer in the architecture and therefore controllers are re-using these functions. When I started to explore how to extend the default API responses, the most obvious extension points are the controllers – just inherit from the original controller and create a new one with the extension. In my opinion, this is not the best way because we need to touch all the controllers in this case and publish our own endpoints next to the original endpoints.