feat: Simple Kubernetes TokenReview identity object

[guicassolato]

Makes the Kubernetes TokenReview-based identity method to always fill the identity object from the status field of the TokenReview response, as opposed to the current hybrid behaviour of trying to detect whether the verified access token is a JWT or an opaque token.

Closes #394.

---

Warning! This is a breaking change and users of Authorino Kubernetes identity verification method must consider its impact to existing AuthConfigs before upgrading to a new version.

Users relying on JWT detection can still extract, decode and parse the JWT directly from the Authorization header. Here’s an example extending the identity object^*:

spec:
  identity:
  - name: k8s-tokenreview
    kubernetes:
      extendedProperties:
      - name: jwt
        valueFrom:
          authJSON: context.request.http.headers.authorization|@extract:{"pos":1}|@extract:{"sep":".","pos":1}|@base64:decode|@fromstr

^{* Requires #401.}

Verification steps

① Deploy

make local-setup FF=1
kubectl port-forward deployment/envoy 8000:8000 2>&1 >/dev/null &

② Follow the steps of the Authentication with Kubernetes tokens (TokenReview API) user guide from step 5

[eguzki]

verification steps working