chore: create proxy model

Author: abhinavs1920

packages/apidash_core/lib/models/models.dart

@@ -1,3 +1,4 @@
 export 'environment_model.dart';
 export 'http_request_model.dart';
 export 'http_response_model.dart';
+export 'proxy_settings_model.dart';

packages/apidash_core/lib/models/proxy_settings_model.dart

@@ -0,0 +1,18 @@
+import 'package:freezed_annotation/freezed_annotation.dart';
+import 'package:json_annotation/json_annotation.dart';
+
+part 'proxy_settings_model.freezed.dart';
+part 'proxy_settings_model.g.dart';
+
+@freezed
+class ProxySettings with _$ProxySettings {
+  const factory ProxySettings({
+    @Default('') String host,
+    @Default('') String port,
+    String? username,
+    String? password,
+  }) = _ProxySettings;
+
+  factory ProxySettings.fromJson(Map<String, dynamic> json) =>
+      _$ProxySettingsFromJson(json);
+}