fix(muc): serialize e2e roominfo as string in disco#info

mod_vnc_e2ehints put the raw boolean returned by get_e2e() (false when
unset) into the disco#info roominfo formdata. muc#roominfo_e2e is a
text-single field, and util.dataforms/util.stanza cannot serialize a
boolean field value, so room:get_disco_info() raised an error and the
server silently dropped the disco#info reply for every existing room
(confirmed at the wire level: non-existent rooms returned item-not-found,
existing rooms returned nothing). Coerce the value to a string, matching
the working mod_vnc_muc_data pattern. get_e2e() itself is left returning a
boolean since the muc-config-form boolean field needs it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Part-of: <http://gitlab.vnc.biz/uxf/vnctalk-prosody/-/merge_requests/3>

vnctalk/mod_vnc_e2ehints.lua

@@ -50,5 +50,10 @@ module:hook("muc-disco#info", function (event)
 	table.insert(form, {
 		name = "muc#roominfo_e2e",
 	});
-	formdata["muc#roominfo_e2e"] = e2e;
+	-- formdata values must be strings: this is a text-single field (no type),
+	-- and util.dataforms/util.stanza cannot serialize a raw boolean as a
+	-- field value. get_e2e() returns a boolean (false when unset), so an
+	-- unconverted value broke room:get_disco_info() for every existing room
+	-- and the server silently dropped the disco#info reply.
+	formdata["muc#roominfo_e2e"] = tostring(e2e);
 end);