mod_muc_moderation: Use reserved nickname as fallback When moderation is invoked from a JID that is not joined, the nickname is not known, but we should include it in the broadcast for transparency.

This module blocks configured queries that change server state.

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

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