Add NTLM authentication support to Http Client

[cesargb]

This pull request introduces NTLM authentication support for the Laravel HTTP Client, extending its capabilities for integrations with services that require this authentication method (e.g., certain Microsoft services or legacy APIs).

The implementation leverages Guzzle’s built‑in NTLM option: https://docs.guzzlephp.org/en/stable/request-options.html?highlight=ntlm

Example usage:

$response = HTTP::withNtlmAuth($username, $password)->post(/* ... */);

[shaedrich]

Suggested change

	/**
	* Specify the digest authentication username and password for the request.
	*
	* @param string $username
	* @param string $password
	* @return $this
	*/
	public function withNtlmAuth($username, $password)
	{
	return tap($this, function () use ($username, $password) {
	$this->options['auth'] = [$username, $password, 'ntlm'];
	});
	}
	/**
	* Specify the authentication username and password for the request.
	*
	* @param string $username
	* @param string $password
	* @param string|null $type
	* @return $this
	*/
	public function withAuth($username, $password, $type)
	{
	return tap($this, function () use ($username, $password) {
	$this->options['auth'] = $type !== null
	? [$username, $password, $type]
	: [$username, $password];
	});
	}
	/**
	* Specify the digest authentication username and password for the request.
	*
	* @param string $username
	* @param string $password
	* @return $this
	*/
	public function withNtlmAuth($username, $password)
	{
	return $this->withAuth($username, $password, 'ntlm');
	});
	}

[shaedrich]

we could even go a step further and validate the type:

    /**
     * @var string[]
     */
    const SUPPORTED_AUTH_TYPES = ['ntlm', 'digest'];

    /**
     * Specify the authentication username and password for the request.
     *
     * @param  string  $username
     * @param  string  $password
     * @param  value-of<SUPPORTED_AUTH_TYPES>|null  $type `null` means 'basic'
     * @return $this
     */
    public function withAuth($username, $password, $type)
    {
		if ($type !== null && !in_array($type, self::SUPPORTED_AUTH_TYPES) {
			throw new Exception(sprintf(
				'Auth type "%s" not supported. Use one of: %s',
				$type,
				implode(', ', self::SUPPORTED_AUTH_TYPES),
			));
		}

        return tap($this, function () use ($username, $password) {
            $this->options['auth'] = $type !== null
            	? [$username, $password, $type]
            	: [$username, $password];
        });
    }

[GrahamCampbell]

Note that this is broken if ext-curl is not installed.