I'd like to re-open this based on the discussion around PUP-4080.
If we're now extending core types with useful features, perhaps I can stop maintaining this thing.
Pull request added which has been rebased against the current HEAD
Yeah I'm not sure why we wouldn't want platform-neutral provider support for core types also in core. I'm +1 on taking this.
FYI, I've added some additional work to the upstream at https://github.com/onyxpoint/puppet-gpasswd that you might want to re-incorporate.