The function '_get_root' tries to retrieve the
hostedzone iterating the domains, eg:
1. srv.prod.example.com
2. prod.example.com
3. example.com
This doesn't work if '_acme-challenge' is in it's
own hostedzone for security reasons.
Starting that iteration with '_acme-challenge.srv.prod.example.com'
fixes this issue.
+ShellCheck
+ACME v2 compatible
Example:
- Fist create 2 new TXT records on _acme-challenge.example.com
- Now note the ID in (...) from the edit page behind "_acme-challenge.example.com"
export SELFHOSTDNS_USERNAME=myname
export SELFHOSTDNS_PASSWORD=mypass
export SELFHOSTDNS_RID=id_of_txt_record
export SELFHOSTDNS_RID2=id_of_second_txt_record
acme.sh --issue -d example.com --dns dns_selfhost