create toAlarm and fromAlarm

lib/model/requests/create_fixed_time_alarm_request.dart

@@ -1,9 +1,17 @@
 import '../alarm/alarm.dart';
+import '../alarm/fixed_time_alarm.dart';
 import 'create_alarm_request.dart';
 
 class CreateFixedTimeAlarmRequest extends CreateAlarmRequest {
   final DateTime? triggerAt;
 
-  CreateFixedTimeAlarmRequest({this.triggerAt})
+  const CreateFixedTimeAlarmRequest({this.triggerAt})
     : super(alarmType: AlarmType.timeFixed);
+
+  CreateFixedTimeAlarmRequest.fromAlarm(FixedTimeAlarm alarm)
+    : triggerAt = alarm.triggerAt,
+      super(alarmType: AlarmType.timeFixed);
+
+  FixedTimeAlarm toFixedTimeAlarm(String id) =>
+      FixedTimeAlarm(id: id, triggerAt: triggerAt!);
 }

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!);
 }

lib/model/requests/create_relative_time_alarm_request.dart

@@ -1,9 +1,17 @@
 import '../alarm/alarm.dart' show AlarmType;
+import '../alarm/relative_time_alarm.dart';
 import 'create_alarm_request.dart';
 
 class CreateRelativeTimeAlarmRequest extends CreateAlarmRequest {
   final DateTime? triggerAt;
 
-  CreateRelativeTimeAlarmRequest({this.triggerAt})
+  const CreateRelativeTimeAlarmRequest({this.triggerAt})
     : super(alarmType: AlarmType.timeRelative);
+
+  CreateRelativeTimeAlarmRequest.fromAlarm(RelativeTimeAlarm alarm)
+    : triggerAt = alarm.triggerAt,
+      super(alarmType: AlarmType.timeRelative);
+
+  RelativeTimeAlarm toRelativeTimeAlarm(String id) =>
+      RelativeTimeAlarm(id: id, triggerAt: triggerAt!);
 }