public function validatePassword ($postPassword1, $postPassword2) {
        $passwordLength = mb_strlen($postPassword1);
        if ($passwordLength < 3) || ($passwordLength > 20)) {
            throw new ValidationException('hasło musi miec 3-20 znakow');
        }

        if ($postPassword1 !== $postPassword2) {
            throw new ValidationException('hasła nie sa takie same');
        }

        $password_hash = password_hash($postPassword1, PASSWORD_DEFAULT);
        return $password_hash;
    }