/**
  * Creates an account identifier with the strategy and the unique userID.
  *
  * @param \Hfrahmann\Opauth\Opauth\Response $opauthResponse
  * @return string
  * @throws \Hfrahmann\Opauth\Exception
  */
 public function createAccountIdentifier(\Hfrahmann\Opauth\Opauth\Response $opauthResponse)
 {
     if ($opauthResponse == NULL) {
         throw new \Hfrahmann\Opauth\Exception("OpauthResponse cannot be NULL.", 1381596920);
     }
     $strategy = $opauthResponse->getStrategy();
     $userID = $opauthResponse->getUserID();
     if (strlen($strategy) > 0 && strlen($userID) > 0) {
         return $strategy . ':' . $userID;
     } else {
         throw new \Hfrahmann\Opauth\Exception("No Strategy or UserID given.", 1381596915);
     }
 }