EventTransform: Support OIDC and authz

Problem

JSONata EventTransform doesn't yet support OIDC and EventPolicy, we should add support for it

The transform-jsonata data plane is in this repo: https://github.com/knative-extensions/eventing-integrations/tree/main/transform-jsonata, there we need to:

• verify JWT tokens given the audience in an environment variable and the key set in a mounted configmap
• verify authorized subjects passed in a mounted configmap

Once the data plane part is complete, we would need to configure it in the EventTransform reconciler and when we create resources

Exit Criteria

• JSONata EventTransform sets the audience in the addressable status (Verified with end to end test)
• JSONata EventTransform verifies JWT tokens (Verified with end to end test)
• JSONata EventTransform prevents unauthorized access as configured with EventPolicies (Verified with end to end test)

Time Estimate (optional):
How many developer-days do you think this may take to resolve?

10-30

Additional context (optional)

• https://knative.dev/development/eventing/transforms/
• https://knative.dev/docs/eventing/features/sender-identity/
• https://knative.dev/docs/eventing/features/authorization
• See issues in projects for similar and related issues https://github.com/orgs/knative/projects/66

Start in the transform-jsonata data plane and review how it can use the audience environment variable and mounted ConfigMaps for JWT and subject verification. Then read pkg/reconciler/eventtransform/eventtransform.go and resources_jsonata.go to see how the reconciler creates and configures resources. Done means the audience appears in addressable status and end-to-end tests verify JWTs and EventPolicy authorization.