public function endpointUrl($prefix = null, $includeId = true)
    {
        $url = self::API_URL;

        // push company id
        if ($includeId) {
            $url = $url .'/'. $this->getCompanyId();
        }

        // push prefix
        if ($prefix = trim($prefix, '/')) {
            $url = $url .'/'. $prefix;
        }

        return $url;
    }