mod_http_oauth2: Apply refresh token ttl to refresh token instead of grant The intent in 59d5fc50f602 was for refresh tokens to extend the lifetime of the grant, but the refresh token ttl was applied to the grant and mod_tokenauth does not change it, leading to the grant expiring regardless of refresh token usage. This makes grant lifetimes unlimited, which seems to be standard practice in the wild.

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
```