Add selfhost.eu to dns validation for letsencrypt

Feature Requests
1

Provider www.selfhost.de.eu also offers letsencrypt.org updates via dns validation.

Either
curl -X POST -F ‘username=%USERNAME%’ -F ‘password=%PASSWORD%’ -F ‘rid=%RECORDID%’ -F ‘content=%CONTENT%’ https://selfhost.de/cgi-bin/api.pl

Or

https://selfhost.de/cgi-bin/api.pl?username=%USERNAME%&password=%PASSWORD%&rid=%RECORDID&content=%CONTENT%

Please add the to the AddOn in the template.