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

[jensbjorgensen]

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 entry_points 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!

[jensbjorgensen]

ping. no interest in merging this?

[jensbjorgensen]

it'd be super cool to get this merged in, the module is at the moment not working with current certbot