title: Firebase Cloud Messaging request DeviceID without connecting to Firebase
body: <p>I am using ionic and <a href="https://github.com/dpa99c/cordova-plugin-firebasex" rel="nofollow noreferrer">firebasex</a> to develop an app that uses Firebase Cloud Messaging. Is there a way to request the device id, without connecting to firebase? I need this, because to be compliant with GDPR, users have to be able to opt out of getting Push Notifications. I want to store the information about which device is opted out in my database though, for which it would be nice to know the device id, so that users could opt in to push notifications in other ways than through my app later.</p>