Client assertion signing is algorithm-agnostic, but the fixtures only
produced RS256 keys, so nothing proved it. Covers RSA, ECDSA and Ed25519,
including both RFC 9864 identifiers.
Also drops a kty assignment that jwx ignores and that would have mislabelled
non-RSA keys had it taken effect.
Some providers require that the `typ` header has a value exactly equal
to `client-authentication+jwt` in accordance with changes introduced by
RFC7523bis.
This commit allows for opting in to setting the `typ` header with this new value.
The default behaviour is to use the previous de facto standard value, `JWT`.
Once the changes in RFC7523bis lands in the affected standards and
identity providers start supporting the new `typ` header (Entra ID being
notable for not supporting this as of this commit), we will default to
use `client-authentication+jwt`.
In accordance with OpenID Connect 1.0 Core, draft 36 incorporating
errata set 3:
> aud
> REQUIRED. Audience. The aud (audience) Claim. [...] The Audience value MUST be the OP's Issuer Identifier passed as a string, and not a single-element array.
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.