NEW(ish): security/acme-client

[Stuart Henderson]

I generally prefer to use acme-client than the python or bash+openssl(1)
monstrosities to fetch SSL certificates, but I have some systems where
I need to use the DNS-01 challenge type which was removed from the
version in base.

Any objections or OKs to adding a port for Kristaps' original version
(attached)?

acme-client.tgz
Description: Binary data