discoverServices method
Resolves the RFCOMM services advertised by device id via SDP, optionally
filtered to a single serviceUuid.
Implementation
@override
Future<List<BluetoothService>> discoverServices(
DeviceId device, {
Uuid? serviceUuid,
}) async {
final all = services[device] ?? const [];
if (serviceUuid == null) return all;
return all.where((s) => s.uuid == serviceUuid).toList();
}