currently we support:
- Linux/Unix users stored in shadow/passwd files
- Pure-FTPd virtual users generated using `pure-pw` CLI
- ProFTPD users generated using `ftpasswd` CLI
using something like this:
update-user <user-id> <username> --public-keys ''
the public keys auth will be disabled
using something like this:
update-user <user-id> <username> --password ''
the password auth will be disabled
we can now have permissions such as these ones
{"/":["*"],"/somedir":["list","download"]}
The old permissions are automatically converted to the new structure,
no database migration is needed
