Add support for purl

[stevespringett]

Thanks for the hard work on Avid DB.

Generally, models have identity and Package URL is a specification that can 1) locate, and 2) identify a package. This is extended to models as well.

This ask is to add support for purl. The major use case of this is to describe models in an SBOM such as the ML-BOM support in CycloneDX, consume and analyze those SBOMs in systems like Dependency-Track, which in the future could support Avid DB. But in order to do so, the models need an identity, thus purl.

See https://github.com/package-url/purl-spec/blob/master/PURL-TYPES.rst#huggingface

[stevespringett]

cc: @nscuro