mod_rest: Use logger of HTTP request in trunk In Prosody trunk rev c975dafa4303 each HTTP request gained its own log sink, to make it easy to log things related to each request and group those messages. Especially where async is used, spreading the request and response apart as mod_rest does with iq stanzas, this grouped logging should help find related messages.

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
```