Make QOAuthHttpServerReplyHandler work with HTTPS

Currently, QOAuthHttpServerReplyHandler only works with HTTP protocol, not HTTPS.
Apparently, some web apps only allow HTTPS as callback URI protocol (Bungie for example).

The current workaround is to not specify the protocol at all in the web app (such that only 'localhost:1234' is the callback URL), and manually intercept the navigation request (in WebEngineView for example) and manually prepend "http://" to the URI.

Normal browsers would probably assume HTTP if no protocol is given, but using an in-app browser (again, WebEngineView) won't assume any protocol and the request is failed.