Add the ability to choose the ACME-DNS server

Needed for self-hosted servers.

dns_scripts/dns_add_acmedns

@@ -9,16 +9,18 @@ apiuser=${ACMEDNS_API_USER:-''}
 apikey=${ACMEDNS_API_KEY:-''}
 apisubdomain=${ACMEDNS_SUBDOMAIN:-''}
 
-# This script adds a token to acme-dns.io DNS for the ACME challenge
-# usage dns_add_acme-dns "domain name" "token"
-# return codes are;
+# This script adds a token to an ACME DNS (default to acme-dns.io) for the ACME challenge
+# usage: dns_add_acme-dns "domain name" "token"
+# return codes are:
 # 0 - success
 # 1 - error returned from server
 
 fulldomain="${1}"
 token="${2}"
 
-API='https://auth.acme-dns.io/update'
+# You can set the env var ACMEDNS_URL to use a specific ACME-DNS server
+# Otherwise we use acme-dns.io
+API=${ACMEDNS_URL:-'https://auth.acme-dns.io'}/update
 
 # Check initial parameters
 if [[ -z "$fulldomain" ]]; then