pulp-certguard needs to move away from unmaintained python-rhsm module

[ggainey]

This code:

https://github.com/pulp/pulpcore/blob/main/pulp_certguard/app/models.py#L184

relies on python-rhsm to check path validity. That module is no longer maintained. Pulp should "own" the code for this - work with the subscription-manager team to get the piece(s) we need and build it into -certguard.

Discussion already in-progress internally.

(Secondary/tangential question - maybe use python-crypto instead of using OpenSSL directly for certguard?)