/**
  * @param array $settings
  * @param array $parameters
  */
 public function authCallback($settings = array(), $parameters = array())
 {
     $error = parent::authCallback($settings, $parameters);
     if (empty($error)) {
         // Now post to the metadata URL
         $data = $this->makeRequest('https://login.mailchimp.com/oauth2/metadata');
         return $this->extractAuthKeys($data, 'dc');
     } else {
         return $error;
     }
 }
 /**
  * Retrieves and stores tokens returned from oAuthLogin.
  *
  * @param array $settings
  * @param array $parameters
  *
  * @return bool|string false if no error; otherwise the error string
  */
 public function authCallback($settings = [], $parameters = [])
 {
     // Constanct Contact doesn't like POST
     $settings['method'] = 'GET';
     return parent::authCallback($settings, $parameters);
 }