[9.x] Http Client: provide pending request to retry callback

[gdebrauwer]

In a couple of our projects, we are using the retry method of the Http Client to handle authentication errors. If a 401 error is thrown, we request a new token and then retry.
To achieve this, we currently have to manually create a request variable and pass the variable inside the closure in order to modify the request and set a new token on the request.

($request = Http::baseUrl(...))
  ->withToken($this->getToken())
  ->retry(2, 0, function ($exception) use ($request) {
      if ($exception->response->status() !== 401) {
          return false;
      }
  
      $request->withToken($this->getNewToken());
  
      return true;
  })
  ->get('...');

This PR allows you to access the request as a parameter of the closure:

Http::baseUrl(...)
  ->withToken($this->getToken())
  ->retry(2, 0, function ($exception, $request) { 
      if ($exception->response->status() !== 401) {
          return false;
      }
  
      $request->withToken($this->getNewToken());
  
      return true;
  })
  ->get('...');

[taylorotwell]

@gdebrauwer It seems surprising to me that this works. Aren't the options given to sendRequest already built? I wouldn't expect modifying the request to actually change them.

[gdebrauwer]

The sendRequest method is called every time the request is retries. The $options array paramer only contains querystring data or request body data. It merges that $options array with $this->options in the sendRequest method. Methods on the PendingRequest, like the withToken method, make changes to that $this->options array, so that's why it works 🙂

[taylorotwell]

@gdebrauwer can you resolve the conflicts on this PR?