public function createUser($username, $password, $firstName, $lastName, array $roleIdentifiers = null, $authenticationProviderName = null)
    {
        $user = new User();
        $name = new PersonName('', $firstName, '', $lastName, '', $username);
        $user->setName($name);

        return $this->addUser($username, $password, $user, $roleIdentifiers, $authenticationProviderName);
    }