Add support for XEP-0410: MUC Self-Ping (Schrödinger's Chat)

Description

XEP-0410 is mostly for clients to implement, but does describe one server-sided optimization. Openfire should implement that optimization.

https://xmpp.org/extensions/xep-0410.html

Environment

None
Fixed

Assignee

Guus der Kinderen

Reporter

Guus der Kinderen