Is your feature request related to a problem? Please describe.

Currently HttpRequestManager only send the response's body to the callback. However, our use case requires to know the response's ContentType to parse the body correctly, or its headers for the internal http cache. It would be helpful if the Http manager exposes Aws::Http::HttpResponse object which already stores all those information through a callback, similar to the current Callback or TextCallback in the Http Parameter and TextParameter respectively. But I'm not sure if there are any implications for the proposed change though.

Describe the solution you'd like

Would that be possible to implement another AddRequest*() member function family in the HttpRequestorRequests class with the callback accepting Aws::Http::HttpResponse as its parameter? If we agree with the solution, I can definitely help to implement it and submit the PR back