Add sound name to remote notifications for iOS

[Fenrikur]

In order to be able to play custom sounds on iOS devices, the FCM push notification should have the "sound" key of its "notification" property set to "notification_default.caf".

Example for event type announcement:

{ 
	"data": {
		"event": "announcement",
		"announcement_id": "i-am-an-announcement-uuid"
	},
	"notification": {
		"title": "Fancy Notification",
    		"body": "This is a very fancy notification!",
	    	"sound": "notification_default.caf"
	},
	"content_available": true,
	"priority": "high"
}

[Fenrikur]

Forgot to mention, that announcement was only intended as an example.
It would be great to have notification (for private messages) follow the same pattern. Also including (if the notification banner should be more informative than "New Private Message") an appropriate title and body in the notification object.

(The sync object should of course stay as it is, without any notification part, to keep it silent and background-y. (: )

[Pinselohrkater]

@Fenrikur Should the sound property for notification(private messages) also benotification_default.caf` , or something else?

Also, it is by design that the body/title payload does not contain the actual private message, but just a link to the app - we want to track who has received/read them, and not 'leak' any information through the notification.

[Fenrikur]

All remote notifications, which should not be silent per se, should use notification_default.caf, as it is an alias that will be mapped to the selected sound locally. Right now, we do not differentiate between announcement and notification content types, when it comes to sounds.

What do you mean by 'link to the app'?

[Pinselohrkater]

Link to the app not as in "link as payload" but as expected behavior. The notification should just open the app, where the user can then get more information.