I'm trying to implement a push notification system on my site, and the documentation says that I need to store the PushSubscription object returned by the PushManager.subscribe method in the database.

The problem is that in the documentation the PushSubscription object does not have an auth property (as shown here), but when I console.log the object returned by the PushManager.subscribe method, it does have that field.

Something like this:

{
  "endpoint":"https://fcm.googleapis.com/fcm/send/cg6PtxFx...",
  "expirationTime":null,
  "keys":{
    "p256dh":"BKvv8i80Eqai6TnPhviquFhrKDdvHXPWkPWNjLtVuE7oxt...",
    "auth":"BX2FxMZMAk0VUivVlxWRzw"
  }
}

Where can I find more info about the keys field of the PushSubscription object?