PendingRequest
Include fastly/http/request.h to use this class.
A handle to a pending asynchronous request returned by Request::send_async() or Request::send_async_streaming().
A handle can be evaluated using PendingRequest::poll(), PendingRequest::wait(), or http::select. It can also be discarded if the request was sent for effects it might have, and the response is unimportant.
