title: Send to all users with a specific language in Firebase Messaging
body: <p>In the Firebase Console it is possible to target devices using a specific app, language, version and user properties. Is it somehow possible to do the same with the API? Or is creating topics the only way to solve bulk sending notifications?</p>
  
  <p>Basically what I would like to do is send a notification to all users with a specific language. I would use the console, but I need to set a click_action / category and that's not supported in the console (as far as I know).</p>