created alarm models

lib/model/location_alarm.dart

@@ -0,0 +1,33 @@
+import 'alarm.dart';
+import 'location.dart';
+
+class LocationAlarm implements Alarm {
+  @override
+  final String id;
+
+  final Location location;
+
+  final int radiusMeters;
+
+  const LocationAlarm({
+    required this.id,
+    required this.location,
+    required this.radiusMeters,
+  });
+
+  factory LocationAlarm.fromJson(Map<String, dynamic> json) {
+    return LocationAlarm(
+      id: json['id'] as String,
+      location: Location.fromJson(json['location'] as Map<String, dynamic>),
+      radiusMeters: json['radiusMeters'] as int,
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return {
+      'id': id,
+      'location': location.toJson(),
+      'radiusMeters': radiusMeters,
+    };
+  }
+}