Added screen to update server

lib/models/update_available.dart

@@ -0,0 +1,55 @@
+import 'package:adguard_home_manager/constants/enums.dart';
+
+class UpdateAvailable {
+  LoadStatus loadStatus = LoadStatus.loading;
+  UpdateAvailableData? data;
+
+  UpdateAvailable({
+    required this.loadStatus,
+    required this.data
+  });
+}
+
+class UpdateAvailableData {
+  String currentVersion;
+  final String newVersion;
+  final String announcement;
+  final String announcementUrl;
+  final bool canAutoupdate;
+  final bool disabled;
+  String? changelog;
+  bool? updateAvailable;
+
+  UpdateAvailableData({
+    required this.currentVersion,
+    required this.newVersion,
+    required this.announcement,
+    required this.announcementUrl,
+    required this.canAutoupdate,
+    required this.disabled,
+    this.changelog,
+    this.updateAvailable
+  });
+
+  factory UpdateAvailableData.fromJson(Map<String, dynamic> json) => UpdateAvailableData(
+    currentVersion: json["current_version"],
+    newVersion: json["new_version"],
+    announcement: json["announcement"],
+    announcementUrl: json["announcement_url"],
+    canAutoupdate: json["can_autoupdate"],
+    disabled: json["disabled"],
+    changelog: json["changelog"],
+    updateAvailable: json['update_available']
+  );
+
+  Map<String, dynamic> toJson() => {
+    "current_version": currentVersion,
+    "new_version": newVersion,
+    "announcement": announcement,
+    "announcement_url": announcementUrl,
+    "can_autoupdate": canAutoupdate,
+    "disabled": disabled,
+    "changelog": changelog,
+    "update_available": updateAvailable
+  };
+}