Frontend first draft

frontend/pshared/lib/api/responses/error/connectivity.dart

@@ -0,0 +1,13 @@
+class ConnectivityError implements Exception {
+  final int? code;
+  final String message;
+
+  const ConnectivityError({this.code, required this.message});
+
+  @override
+  String toString() {
+    return code == null 
+      ? 'Error response, message: $message)' 
+      : 'Error response (code: $code, message: $message)';
+  }
+}