code: public function handle(ServerRequestInterface $request, ServerFrame $frame) : ResponseInterface
      {
          try {
              return $frame->next($request);
  
          } catch (HttpException $httpException) {
  
              // forward to login page for unauthorized urls
              if ($httpException instanceof HttpUnauthorized) {
                  return $frame->responseFactory()->create(302)->withHeader('Location', $this->loginUri);
              }
  
              return $frame->responseFactory()->create(
                  $httpException->getCode(),
                  [],
                  $httpException->getCode() . ' ' . $httpException->getMessage() . ': ' . $httpException->getInfo()
              );
          }
      }
docs: @param ServerRequestInterface $request
  @param ServerFrame            $frame
  
  @return ResponseInterface