public function createPaymentForm(array $params)
    {
        $params = array_replace_recursive(
            [
                'billId'       => null,
                'publicKey'    => null,
                'amount'       => null,
                'successUrl'   => null,
                'customFields' => [],
            ],
            $params
        );

        $params['amount'] = $this->normalizeAmount($params['amount']);
        $params['customFields']['apiClient']        = CLIENT_NAME;
        $params['customFields']['apiClientVersion'] = CLIENT_VERSION;

        return self::CREATE_URI.'?'.http_build_query($params, '', '&', PHP_QUERY_RFC3986);

    }