I did a number of things here:

the *add, *mod, and *del utilities, as well as id recieved substantial
changes, probably what you'd call a rewrite. This was of course using
clap-rs. These should all be very stable at this point (except
unimplemented features in usermod, grr)

getty, passwd, and su are simply ported, using clap for arg parsing. I
didn't change any of the logic, just swapped ArgParser for clap.

Fixed a bug with passwd and unset passwords

I'll open issues about the ones I didn't mention.