$user->login()

$user->login(string $password, \Kirby\Session\Session|array|null $session = null): bool

// simple login form submission example
if($username = get('username') and $password = get('password')) {

  $user = $kirby->user($username);

  if($user and $user->login($password)) {
    // redirect to the homepage
    // or any other page
    go();
  } else {
    echo 'invalid username or password';
  }

}

// put the login form with username and
// password field down here.