update to work with certbot 2.8.0 (requires different command-line args)

the plugin no longer works with certbot when I installed it recently (2.8.0). I wasn't intimate with the plugin architecture before now, but looking at the current code and documentation the plugin name is whatever the name specified in the package entrypoints definition. Those names were "auth" and "installer". The name "auth" cannot work at all against current certbot because it breaks inside their (buggish) argument pre-parser which picks out "auth" as a verb instead of an argument to '-a'. Beyond that though since there's no longer a package-name qualifier attached "auth" and "installer" seem a bit too generic, so I prepended these with "s3front". This does mean that the command-line args are broken for previous but I didn't think forcing the "package_name:" on the front of them was a great option either since it kind of infers/pretends that the plugin mechanism works the same as it did.

Aside from plugin naming the certbot internals also now filter plugins according to interfaces they implement so I needed to add that otherwise they get filtered out. Aside from that everything seems to still work great! Thanks for creating this very useful bit of software!

dlapiduz / certbot-s3front

update to work with certbot 2.8.0 (requires different command-line args) #95