Packager type

We require a Packager Type that describes the packager that built a package. See repod's implementation for reference: https://gitlab.archlinux.org/archlinux/repod/-/blob/cc0e43c7c858c679027068639e7db554fb78aa21/repod/common/models.py#L326-363

As this should describe a PackagerName and an Email address as part of a UserID it will likely end up being a compound type.