Add HeaderKind to enable setting request headers

[adam-cattermole]

In the wasm-shim refactor the request vs response headers that was fixed prior (#143) was missed. I've introduced an enum called HeaderKind which explicitly differentiates the Request vs Response types for the specific actions, and have enforced that these can only be added at the correct phase.

I've updated the authconfig to add request headers, so this is verifiable as follows:

make local-setup

kubectl port-forward --namespace kuadrant-system deployment/envoy 8000:8000

curl -H "Host: test.a.auth.com" -H "Authorization: APIKEY IAMALICE" http://127.0.0.1:8000/get -i

See My-Header in the echoed request:

HTTP/1.1 200 OK
content-type: application/json
server: envoy
date: Wed, 05 Feb 2025 16:10:52 GMT
content-length: 545
x-envoy-upstream-service-time: 2

{
  "method": "GET",
  "path": "/get",
  "query_string": null,
  "body": "",
  "headers": {
    "Host": "test.a.auth.com",
    "User-Agent": "curl/8.7.1",
    "Accept": "*/*",
    "Authorization": "APIKEY IAMALICE",
    "X-Forwarded-For": "10.244.0.10",
    "X-Forwarded-Proto": "http",
    "X-Envoy-Internal": "true",
    "X-Request-Id": "9641a263-bfdb-49b7-b1c2-a7662ec1e74e",
    "My-Header": "{\"my-key\":true}",
    "X-Envoy-Expected-Rq-Timeout-Ms": "15000",
    "Version": "HTTP/1.1"
  },
  "uuid": "fbbaad8b-2d15-42b1-9c3d-c21721d37b59"
}

Resolves #164

[adam-cattermole]

These have been renamed and are Option that is initialised once and extended until it is taken. Crucially if this is None it can no longer be initialised, we have added the headers and we are no longer in the correct phase

[didierofrivia]

🍸