code: public function onBootstrap(MvcEvent $e)
      {
          if (!$e->getRequest() instanceof HttpRequest) {
              return;
          }
  
          $app = $e->getApplication();
          $services = $app->getServiceManager();
  
          $eventManager       = $app->getEventManager();
          $sharedEventManager = $eventManager->getSharedManager();
  
          $sharedEventManager->attach(UserService::class, 'register', function($e) use ($services)
          {
              $user = $e->getParam('user');
              if ($user instanceof RoleableInterface &&
                  $services->has(AuthorizationModuleOptions::class)
              ) {
                  /* @var $config PermissionsModuleOptions */
                  $config = $services->get(PermissionsModuleOptions::class);
                  $roleClass = $config->getRoleEntityClass();
                  $mapper = $services->get('MapperManager')->get($roleClass);
                  if ($defaultRole = $mapper->find($config->getAuthenticatedRole())) {
                      $user->addRole($defaultRole);
                  }
              }
          }, 100);
      }
docs: Event callback to be triggered on bootstrap
  
  @param MvcEvent $e
  @return void