Add App Identifier to Push Notification Payload

[NikoHadouken]

We have built a custom push gateway to support push notifications for both the official Rocket.Chat app and our white-labeled app. To improve app-specific handling, it would be useful to include the app identifier in the notification payload, allowing the gateway to distinguish which app the notification is intended for.

Currently, the app identifier is already included in the payload send to the APN endpoint because there it is used as topic, but it is left out for the GCM endpoint:

Rocket.Chat/apps/meteor/app/push/server/push.ts

Lines 340 to 348 in c5f6734

	if ('apn' in app.token && app.token.apn) {
	countApn.push(app._id);
	return this.sendGatewayPush(gateway, 'apn', app.token.apn, { topic: app.appName, ...gatewayNotification });
	}
	if ('gcm' in app.token && app.token.gcm) {
	countGcm.push(app._id);
	return this.sendGatewayPush(gateway, 'gcm', app.token.gcm, gatewayNotification);
	}

Since the field topic is likely intended for notification topics, we propose adding a separate field appName (or similar) to the payload in addition to the topic field.

This allows a push gateway to decide how (or if) to handle a push notification.