Joohoi's ACME-DNS provider for libdns

This package implements the libdns interfaces for Joohoi's ACME-DNS.

ACME-DNS server is meant to be used solely for obtaining HTTPS certificates using DNS-01 challenges. Its API is by design limited - the only operation ACME-DNS allows is updating TXT records of one subdomain associated with ACME-DNS account. There are at most two records and older records are deleted as new ones are appended. Due to these limitations, this libdns provider implements only RecordAppender and RecordDeleted interfaces. And DeleteRecords method is a no-op - it doesn't do anything.

This provider is written mostly for Caddy's acmedns plugin. For more information, see:

1. github.com/caddy-dns/acmedns

2. github.com/joohoi/acme-dns

3. A Technical Deep Dive: Securing the Automation of ACME DNS Challenge Validation