Android: no beacons detected in background

[paolotremadio]

Hey,

I've got your lib installed on my app and what I do is:

  startScanning('UUID HERE', {
    useForegroundService: true,
    useBackgroundScanning: true,

    // Android only
    foregroundTitle: 'Location based automation is active',
    foregroundMessage: 'Checking location in the background to trigger automations',
  });

It works perfectly fine on iOS, I get updates both in foreground and background (that's because it's all handled by CoreLocation). On Android, I do get updates only with the app open in the foreground (that's with useForegroundService set to true or false, it doesn't matter).

My Expo Android permissions are:

[
        "android.permission.INTERNET",
        "android.permission.ACCESS_COARSE_LOCATION",
        "android.permission.FOREGROUND_SERVICE",

        "android.permission.ACCESS_FINE_LOCATION",
        "android.permission.ACCESS_BACKGROUND_LOCATION",
        "android.permission.RECEIVE_BOOT_COMPLETED",
        "android.permission.FOREGROUND_SERVICE_LOCATION",
        "android.permission.BLUETOOTH",
        "android.permission.BLUETOOTH_ADMIN",
        "android.permission.BLUETOOTH_SCAN",
        "android.permission.BLUETOOTH_CONNECT",
        "android.permission.VIBRATE"
]

Any clue on why it doesn't work in the background?

FYI: I've managed to get the plugin running on Expo SDK 50: fb7fb92 - feel free to port the changes in your repo.