protected function withHeaders(array $headers)
    {
        $clean = [];

        foreach ($headers as $key => $value) {
            if (! Str::startsWith($key, ['HTTP_', 'CONTENT_'])) {
                $key = 'HTTP_' . $key;
            }

            $clean[$key] = $value;
        }

        $this->headers = array_merge($this->headers, $clean);

        return $this;
    }