prosodyctl check: Warn about invalid domain names in the config file
This ensures that domain names of virtual hosts and components are valid in
XMPP, and that they are encoded correctly.
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
}