public function add(string $name, string $value): void
    {
        $key = strtolower($name);
        if (!isset($this->headers[$key])) {
            $this->headers[$key] = [$name, $value];

            return;
        }

        $this->headers[$key] = [$name, $this->headers[$key][1] . ', ' . $value];
    }