Firebase Admin .NET SDK v1.8.0

Cloud Messaging

• Added SubscribeToTopicAsync() and UnsubscribeFromTopicAsync() methods to the FirebaseMessaging class for managing topic subscriptions. Thanks Leo-Mepham for the contribution.
• Added support for specifying the analytics label for notifications via AndroidFcmOptions, ApnsFcmOptions and FcmOptions classes. Thanks RannyRanny for the contribution.
• Introduced a new FirebaseMessagingException class and a MessagingErrorCode enum type for improved error handling support. All FCM APIs now throw instances of the FirebaseMessagingException class. This is a subclass of the existing FirebaseException type.