mod_http_oauth2: Implement RFC 7628 Proof Key for Code Exchange
Likely to become mandatory in OAuth 2.1.
Backwards compatible since the default 'plain' verifier would compare
nil with nil if the relevant parameters are left out.
module:hook("authentication-success", function (event)
local session = event.session;
local sasl_handler = session.sasl_handler;
session.log("info", "Authenticated with %s", sasl_handler and sasl_handler.selected or "legacy auth");
end);