sign_in_screen.dart

return Form(
  key: _formKey,
  child: Column(
    mainAxisSize: MainAxisSize.min,
    mainAxisAlignment: MainAxisAlignment.center,
    children: [
      TextFormField(
        controller: _usernameController,
        keyboardType: TextInputType.name,
        decoration: const InputDecoration(
          labelText: 'Username',
          border: OutlineInputBorder(),
        ),
        validator: (value) {
          if (value == null || value.isEmpty) {
            return 'Please enter your username';
          }
          return null;
        },
      ),
      const SizedBox(height: 12),
      TextFormField(
        controller: _passwordController,
        keyboardType: TextInputType.visiblePassword,
        obscureText: true,
        decoration: const InputDecoration(
          labelText: 'Password',
          border: OutlineInputBorder(),
        ),
        validator: (value) {
          if (value == null || value.isEmpty) {
            return 'Please enter your password';
          }
          return null;
        },
      ),
      const SizedBox(height: 12),
      ErrorText(errorMessage: _errorMessage),
      ElevatedButton(
        onPressed: _loginUser,
        child: AppButton(
          buttonText: 'Login',
          isLoading: _isLoading,
        ),
      ),
      const SizedBox(height: 12),
      RichText(
        textAlign: TextAlign.center,
        text: TextSpan(
          text: 'Don\'t have an account?\n',
          style: Theme.of(context).textTheme.caption?.copyWith(
                fontWeight: FontWeight.w700,
              ),
          children: [
            TextSpan(
              text: 'Click here to register.',
              style:
                  Theme.of(context).textTheme.caption?.copyWith(
                        decoration: TextDecoration.underline,
                        fontWeight: FontWeight.w700,
                      ),
              mouseCursor: SystemMouseCursors.click,
              recognizer: TapGestureRecognizer()
                ..onTap = () => context.go('/sign-up'),
            ),
          ],
        ),
      ),
    ],
  ),
);