How can I send basic authentication with request?

Hi there

I am trying to set up a proxy where I pass on the path of the request and send Basic Authentication headers along.

How could I achieve this? I thought something like this should work:

```php
$response = $proxy
->forward($request)
->filter(function ($request, $response, $next) {

$method = 'GET';
$uri = 'http://cms.local.test/api/pages/';

$request = new GuzzleHttp\Psr7\Request(
$method,
$uri,
[
'auth' => ['myusername', 'mypassword]
'Content-Length' => 30000, // a random number? How could I fix this issue that a length is required?
],
$request->getBody()
);

// Proceed with the rest
$response = $next($request, $response);

return $response;
})
->to('http://cms.local.test/api/pages/');

// Output response
(new Zend\HttpHandlerRunner\Emitter\SapiEmitter)->emit($response);
```

If I run this I get 'Unauthenticated', which I would get if I request the given URL without a password and without a username.

Interestingly, if I change the user to a wrong username, I do get `The user \"mywrongusername\" cannot be found`.
So I assume that the whole auth headers are NOT sent along.

How could I send Basic auth to the final URL?

Also I had the problem that I when I create a new guzzle request that I have to repeat the request URL. Is there a smarter way to do that?

Thank you for your help.
cheers

PS:If I leave out the `Content-Length` part I get an error that this is required. What should I set there?