title: Use FCM with another database
body: <p>I am developping a mobile application that must implement push notifications. Documents are stored on a SQL database, and people should be able to edit these docs after downloading them offline, then the modifications should be saved in the SQL Database once the phone is online again. People should be able to receive notifications when the app is closed.</p>
  
  <p>I heard that I need push notifications, and for android there is Firebase Cloud Messaging (FCM). But is it possible to use FCM with my SQL database ?</p>
  
  <p>All tutorials in the docs only speak about connecting the app with Firebase</p>