added devcontainer with all tools for frontent (deno, nextjs) and backend (dart, go)

backend-dart/lib/domain/entities/user.dart

@@ -0,0 +1,13 @@
+class User {
+  final String id;
+  final String name;
+  final String email;
+  final String password;
+
+  User({
+    required this.id,
+    required this.name,
+    required this.email,
+    required this.password,
+  });
+}