Use 127.0.0.1 instead of localhost for redirect_uri in QOAuth2AuthorizationCodeFlow

When I'm using QOAuth2AuthorizationCodeFlow, together with the QOAuthHttpServerReplyHandler, it uses http://localhost:{PORT}/ as the redirect uri. However, in section 8.3 of RFC 8252 (https://tools.ietf.org/html/rfc8252#section-8.3), it is specifically NOT RECOMMENDED to use localhost, but instead to use 127.0.0.1.

I would say that it is better to follow this by default, but at least make it configurable.