create toAlarm and fromAlarm

lib/model/requests/create_location_alarm_request.dart

@@ -1,4 +1,5 @@
 import '../alarm/alarm.dart' show AlarmType;
+import '../alarm/location_alarm.dart';
 import '../location.dart';
 import 'create_alarm_request.dart';
 
@@ -9,4 +10,12 @@ class CreateLocationAlarmRequest extends CreateAlarmRequest {
 
   const CreateLocationAlarmRequest({this.location, this.radiusMeters})
     : super(alarmType: AlarmType.location);
+
+  CreateLocationAlarmRequest.fromAlarm(LocationAlarm alarm)
+    : location = alarm.location,
+      radiusMeters = alarm.radiusMeters,
+      super(alarmType: AlarmType.location);
+
+  LocationAlarm toLocationAlarm(String id) =>
+      LocationAlarm(id: id, location: location!, radiusMeters: radiusMeters!);
 }