Utility function to create a new HTTPRequest

MakeHTTPRequest.hpp

template <typename DoneLambda, typename ErrorLambda>
auto MakeHTTPRequest(const std::string& rURL,
                     DoneLambda&& d,
                     ErrorLambda&& e) 
-> HTTPRequest<DoneLambda, ErrorLambda>
{
  return { rURL,
           std::forward<DoneLambda>(d),
           std::forward<ErrorLambda>(e)
         };
}