util.smqueue: Refactor checkpoint logic and add tests The previous checkpoint logic used recursion, and the code was more complex than needed due to maintenance of the self._next_checkpoint field. This switches to a loop, which should be a bit more efficient, partly because there are fewer calls (although it was a tail call) and because table lookups can now be cached between each execution. _call_checkpoints() is now called unconditionally for every ack, which is simpler though adds a function call, it should be more than balanced out by the other changes.

-- XEP-0307: Unique Room Names for Multi-User Chat
local st = require "prosody.util.stanza";
local unique_name = require "prosody.util.id".medium;
module:add_feature "http://jabber.org/protocol/muc#unique"
module:hook("iq-get/host/http://jabber.org/protocol/muc#unique:unique", function(event)
	local origin, stanza = event.origin, event.stanza;
	origin.send(st.reply(stanza)
		:tag("unique", {xmlns = "http://jabber.org/protocol/muc#unique"})
		:text(unique_name():lower())
	);
	return true;
end,-1);