mod_ping_muc: Yet another attempt to improve MUC reliability This time by moving XEP-0410 to the server. Will this save the users from the s2s timeouts? What horrifying unintentional side-effects will this have? Tune in next week to find out!

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```