OIDC Client JWT support

*Description*:

https://github.com/keycloak/keycloak/releases/tag/26.4.0 was just released with:
* Federated Client Authentication to use SPIFFE or Kubernetes service account tokens for client authentication.

I'd like to be able to use jwt tokens from a SPIFFE endpoint or Kubernetes projected jwt token as the client secret instead of a hardcoded one. This would eliminate the need to configure a password at all, and allow short lived tokens to be automatically generated and used for securing this communication channel.