Callback for subscribeToTopic & unsubscribeFromTopic

[arifje]

Feature request; callback for subscribeToTopic and unsubscribeFromTopic, so we can check if the subscription is successful (or not). Missing on Android and iOS if I am correct.

[m1ga]

Good idea! I'll add that to my Android update (https://firebase.google.com/docs/cloud-messaging/android/topic-messaging#subscribe_the_client_app_to_a_topic) 👍

[m1ga]

#115 - for Android:
two events: subscribe and unsubscribe with (un)subscribed:true/false as a callback parameter