feat: extension support (#78)

ui/flutter/lib/api/model/switch_extension.dart

@@ -0,0 +1,16 @@
+import 'package:json_annotation/json_annotation.dart';
+
+part 'switch_extension.g.dart';
+
+@JsonSerializable()
+class SwitchExtension {
+  bool status;
+
+  SwitchExtension({
+    required this.status,
+  });
+
+  factory SwitchExtension.fromJson(Map<String, dynamic> json) =>
+      _$SwitchExtensionFromJson(json);
+  Map<String, dynamic> toJson() => _$SwitchExtensionToJson(this);
+}