Support Flow Control on AWS Gateway

[tanveergill]

What

1. Gateway can work with OPA for authorization. Metadata such as headers and function names get sent to OPA as labels for authorization, refer this blog.
2. The Gateway response can take arbitrary context where we can serialize the CheckResponse message (might need to flatten if it allows only key/value pairs)
3. The context can be emitted in Gateway access logs using custom access logs
4. Aperture Agents can run behind an Ingress Controller and K8s service on a dedicated cluster along with Controller. This cluster can be deployed per AWS region.

[tanveergill]

@krdln, @hasit,

Re-assigned the ticket to Hasit since he has the environment set up for this task