Add the auth credentials to a url (if needed).

def get_url_with_auth(self, url) -> str:
        """Add the auth credentials to a url (if needed)."""
        if not self._username:
            return url

        url += '&user={:s}'.format(self._username)

        if not self._password:
            return url

        return url + '&pass={:s}'.format(self._password)