Notification coalescing on Android is done automatically when we pass to `NotificationManager.notify()` and id that has been passed previously. The OS replaces the previous notification with the new one. That said to support encrypted notifications coalescing we have to:
1. Always provide brand `id` field of the notification.
2. Put the `collapseKey` in the encrypted notification payload.
3. One the device look for the `collapseKey` in the payload after decryption and use it instead of `id` in case it is present.