title: How to disable cloud messaging per device/user in flutter?
body: <p>For a flutter app I’m using Firebase Cloud Messaging and cloud functions to send push notifications to users, using their FCM registration tokens. The app has a settings page where users should be able to turn off certain push notifications. The notifications are user specific, so a topic to subscribe or unsubscribe to wouldn’t work, but the notifications can be classified in certain categories. </p>
  
  <p>For example in a chat app when user A send a message to user B that push notification could be in a category of ‘chat messages’, while user A could also delete the chat with user B and that push notification could be in a category of ‘deleted chats’. </p>
  
  <p>How can I make it so that user B can turn off notifications for ‘deleted chats’, while still receiving notifications for ‘chat messages’? Is it possible to use a condition with a topic and a user’s registration token on one way or the other? Any ideas are greatly appreciated! </p>