mod_rest: Add special handling to catch MAM results from remote hosts Makes MAM queries to remote hosts works. As the comment says, MAM results from users' local archives or local MUCs are returned via origin.send() which is provided in the event and thus already worked. Results from remote hosts go via normal stanza routing and events, which need this extra handling to catch. This pattern of iq-set, message+, iq-result is generally limited to MAM. Closest similar thing might be MUC join, but to really handle that you would need the webhook callback mechanism.

Generate a DNS UPDATE order in format suitable for `nsupdate` based on
current port configuration.

Example output:

```
$ prosodyctl mod_dnsupdate -d example.com -t xmpp.example.com example.com
zone example.com
server ns1.example.com
ttl 3600
add _xmpp-client._tcp.example.com IN SRV 1 1 5222
add _xmpp-server._tcp.example.com IN SRV 1 1 5269
```