Contributing to add JWT-SVID support

[hug-dev]

Hello 👋 !

We are planning to use a SPIFFE-based identity provider and authenticator in Parsec.

We will mostly use the JWT parts of the Workload API and primarly ValidateJWTSVID. It will be used on the Parsec service to validate JWT tokens given by clients.

We were thinking of expanding this crate to add support for that nad making pull-requests for it. And maybe more in the future as we use it 😃!

Would that be ok for you?

[hug-dev]

More precisely we want to add:

• the ability to fetch its JWT-SVID
• the ability to validate a JWT-SVID remotely (faster, for PoC/demos)
• the ability to validate a JWT-SVID locally (for security, will take longer)

Will try to make a PR when I come to this!