code: public function onKernelResponse(FilterResponseEvent $event)
      {
          $response = $event->getResponse();
  
          $response->headers->set('Access-Control-Allow-Origin', '*');
          $response->headers->set('Access-Control-Allow-Credentials', 'true');
          $response->headers->set('Access-Control-Expose-Headers', 'Link');
          $response->headers->set('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE');
  
          $response->headers->set(
              'Link',
              '<' . $this->hydra->getDocumentationUrl() . '>; rel="http://www.w3.org/ns/hydra/core#apiDocumentation"'
          );
      }
docs: Marks request that whose controller return value should be serialized
  by the Hydra serializer
  
  @param FilterControllerEvent $event A FilterControllerEvent instance