code: public function startProcessing(Router $router, Request $request, $uri, $args) : Response
      {
          $params = new ControllerParams($uri, $this->controllerClass, $this->controllerMethod, $args, $router->getServiceContainer());
          
          $request->attributes->set('controller', $params);
          $request->attributes->set('router', $router);
          return $this->process($request);
      }
docs: Start processing this route, by calling middleware in order, and then calling the specified Controller
  This call stores various information (args, controller info) on the Request
  
  @param Router $router   The router calling this handler
  @param Request $request The request for the current route
  @param string $uri      The matched route uri
  @param array $args      The matched arguments from the route
  @return Response