mod_http_xep227: Add support for import via APIs rather than direct store manipulation In particular this transitions PEP nodes and data to be imported via mod_pep's APIs, fixing issues with importing at runtime while PEP data may already be live in RAM. Next obvious candidate for this approach is rosters, so clients get immediate roster pushes and other special handling (such as emitting subscribes to reach the desired subscription state).

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
```