mod_pubsub_serverinfo: Detect existence of pub/sub node Instead of blindly trying to create the pub/sub node to publish items to, a service discovery query is performed to check if node creation is required. Added various bits of warn and debug logging, to give a user better feedback if and why something is failing.

module:hook("authentication-success", function (event)
	local session = event.session;
	local sasl_handler = session and session.sasl_handler;
	local log = session and session.log or module._log
	log("info", "Authenticated with %s", sasl_handler and sasl_handler.selected or "legacy auth");
end);