Adds options to require at least one character to be uppercase,
lowercase, numeric and/or special. Defaults all to off to maintain
compatibility with existing configurations.

There's a lot of different possible complexity policies you
could want, but these feel fairly simple and are based on the
password policy options available in AWS IAM. It will at least
allow you to stop 'password' and 'aaaaaa' being valid passwords!

feat: add password security requirements

This lets us use local files for templates(!), calls mailgun
directly instead of using SMTP, and provides a nice and clean
text representation.

Includes the standard Puzzad template with the required
company information.