The following constants are available globally.
The scope to be used when fetching/deleting a token for Firebase Messaging.
extern NSString *const _Nonnull kFIRInstanceIDScopeFirebaseMessaging
Called when the system determines that tokens need to be refreshed. This method is also called if Instance ID has been reset in which case, tokens and FCM topic subscriptions also need to be refreshed.
Instance ID service will throttle the refresh event across all devices to control the rate of token updates on application servers.
extern NSString *const _Nonnull kFIRInstanceIDTokenRefreshNotification