constructor(props) {
    super(props);

    this.state = {
      username: '',
      password: '',
      errorMessage: null,
    };

    this.resolver = () => null;

    this.handleSignIn = this.handleSignIn.bind(this);
    this.doSignIn = this.doSignIn.bind(this);

    this.handleMFAValidate = this.handleMFAValidate.bind(this);
    this.handleMFACancel = this.handleMFACancel.bind(this);
    this.handleMFASuccess = this.handleMFASuccess.bind(this);
  }
React component for SignIn with support for Multi-Factor Authentication (MFA)