mod_http_oauth2: Switch to '303 See Other' redirects This is the recommendation by draft-ietf-oauth-v2-1-07 section 7.5.2. It is the only redirect code that guarantees the user agent will use a GET request, rather than re-submitting a POST request to the new URL. The latter would be bad for us, as we are encoding auth tokens in the form data.

This module helps make BOSH and WebSocket connection endpoints
discoverable via the HTTP method described in
[XEP-0156](https://xmpp.org/extensions/xep-0156.html#http).