mod_pep: Wipe pubsub service on user deletion
Data is already wiped from storage, but this ensures everything is
properly unsubscribed, possibly with notifications etc.
Clears recipient cache as well, since it is no longer relevant.
Structure of a stanza:
stanza {
--- properties ---
tags -- array of tags
--- static methods ---
iq(attrs) --
--- read-only methods ---
reply -- return new stanza with attributes of current stanza
child_with_name(string name) -- return the first child of the current tag with the matching name
--- write methods ---
tag(name, sttrs) -- create a new child of the current tag, and set the child as current
up() -- move to the parent of the current tag
text(string) -- append a new text node to the current tag
}