HttpRequest::getRequestMessage — Get request message
If redirects were allowed and several responses were received, the data
references the last received response. Use HttpMessage::getParentMessage()
to access the data of previously sent requests within this request cycle.
Note that the internal request message is immutable, that means that the
request message received through HttpRequest::getRequestMessage() will
always look the same for the same request, regardless of any changes you
may have made to the returned object.
Returns an HttpMessage object representing the sent request.
Throws HttpMalformedHeadersException, HttpEncodingException.