code: public function registerCustom(): void
      {
          if (!$fn = $this->group) {
              return;
          }
  
          $this->router->group([], function () use ($fn) {
              $fn(new RouteRegistrar(
                  $this->router,
                  ['controller' => $this->controller()],
                  [self::PARAM_RESOURCE_TYPE => $this->resourceType]
              ));
          });
      }
docs: Register custom routes.
  
  @return void