net.server_epoll: Add support for systemd socket activation
Allows creating listening sockets and accepting client connections
before Prosody starts.
This is unlike normal Prosody dynamic resource management, where ports
may added and removed at any time, and the ports defined by the config.
Weird things happen if these are closed (e.g. due to reload) so here we
prevent closing and ensure sockets are reused when opened again.
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
}