Push Notifications from core

[shuhanmirza]

No description provided.

[meafs]

Commit cd58ebd

To get it working on the app side:
Java code:

FirebaseMessaging.getInstance().subscribeToTopic("Stream").addOnCompleteListener(task -> {
            if (task.isSuccessful()) {
                //Successfully Subscribed to Notification Service
            } else {
                //Subscription  Notification Service failed
            }
        });

[meafs]

I'll complete this task once server issue gets fixed :)