Add login Credentials data class

lib/models/credentials.dart

@@ -0,0 +1,42 @@
+import 'package:flutter_portal/models/exec_error.dart';
+import 'package:result_monad/result_monad.dart';
+
+class Credentials {
+  final String username;
+  final String password;
+  final String serverName;
+
+  Credentials(
+      {required this.username,
+      required this.password,
+      required this.serverName});
+
+  Credentials copy({String? username, String? password, String? serverName}) {
+    return Credentials(
+        username: username ?? this.username,
+        password: password ?? this.password,
+        serverName: serverName ?? this.serverName);
+  }
+
+  static Result<Credentials, ExecError> buildFromHandle(
+      String handle, String password) {
+    final elements = handle.split('@');
+    if (elements.length != 2) {
+      return Result.error(ExecError(
+          type: ErrorType.authentication,
+          message: 'Handle has invalid format: $handle'));
+    }
+    final result = Credentials(
+      username: elements[0],
+      password: password,
+      serverName: elements[1],
+    );
+    print(result);
+    return Result.ok(result);
+  }
+
+  @override
+  String toString() {
+    return 'Credentials{username: $username, password?: ${password.isNotEmpty}, serverName: $serverName}';
+  }
+}