public function deleteRefreshToken(fkooman\OAuth\Client\RefreshToken $refreshToken)
{
$collection = $this->mongo->selectCollection($this->db, 'refresh_tokens');
$result = $collection->remove(array('client_config_id' => $refreshToken->getClientConfigId(), 'user_id' => $refreshToken->getUserId(), 'refresh_token' => $refreshToken->getRefreshToken()));
return is_array($result) && 1 == $result['ok'] && $result['n'] > 0 || $result;
}