public function findUser(LtiLaunchData $ltiContext)
    {
        $ltiConsumer = $ltiContext->getLtiConsumer();
        $taoUserId = $this->getUserIdentifier($ltiContext->getUserID(), $ltiConsumer->getUri());
        if (is_null($taoUserId)) {
            return null;
        }

        $ltiUser = $this->createLtiUser($ltiContext, $taoUserId);

        \common_Logger::t("LTI User '" . $ltiUser->getIdentifier() . "' found.");

        $this->updateUser($ltiUser, $ltiContext);

        return $ltiUser;
    }