code: public function onKernelResponse(FilterResponseEvent $event): void
      {
          if (!$this->framework->isInitialized()) {
              return;
          }
  
          // Fetch remaining headers and add them to the response
          $this->fetchHttpHeaders();
          $this->setResponseHeaders($event->getResponse());
      }
docs: Adds the Contao headers to the Symfony response.