This allows us to verify signatures without relying on heuristics used
by jws.WithInferAlgorithmFromKey() that may introduce security and
performance implications.
There's a bunch of changes here, but in essence:
- split out openid configuration
- separate openid configuration between client/rp and provider
- consolidate client and provider related code in separate packages
These changes allow for simplification of the Handler, as well as a
bunch of test/mock code as the configuration is now instantiated
seperately from the client/provider code.
