public function licenseCheck($license_key, \JaegerApp\License $license)
    {
        if ($license_key == '') {
            $this->setError('license_number', 'missing_license_number');
        } else {
            if (! $license->validLicense($license_key)) {
                $this->setError('license_number', 'invalid_license_number');
            }
        }
        
        return $this;
    }