Support https_only Requests

Right now https_only is something set in the Client when building it, this means that if you have a dynamic runtime configuration you need to either re-build the Client each time, or hold 2 clients and choose between them. It would be nicer if RequestBuilder had that configuration so it could be chosen per request, and not just per Client.

(Specifically, we want to force that if a user used a https scheme, we force the connection to be https, disallowing e.g. A redirection to http.