Eu tenho tentado redirecionar os usuários para a parte "ação" do Webpush vinda do back-end (PHP).

    return (new WebPushMessage)
        ->title('Title')
        ->icon('icon.png')
        ->body('Body Msg')
        ->action('Open Notification', 'open_notification')
        ->data(['id' => $notification->id,'url'=>'http://somewhere']);

Os trabalhadores de serviço padrão usam:

self.addEventListener('notificationclick', function(event) {
    console.log('On notification click: ', event.notification.tag);
    event.notification.close();

    // This looks to see if the current is already open and
    // focuses if it is
    event.waitUntil(clients.matchAll({
       type: "window"
    }).then(function(clientList) {
       for (var i = 0; i < clientList.length; i++) {
          var client = clientList[i];
              if (client.url == '/' && 'focus' in client)
                 return client.focus();
       }
       if (clients.openWindow)
          return clients.openWindow('/');
    }));
});

Dehttps://developer.mozilla.org/en-US/docs/Web/Events/notificationclick

Angular 5 usos

import {SwPush, SwUpdate} from '@angular/service-worker'; 

Minha pergunta então é como interpretar isso no front end (Angular 5) usando @ angular / service-worker