Correctly add auth headers that should be sent to the upstream

[adam-cattermole]

Authorino does not support the following fields in an OkHttpResponse:

• response_headers_to_add
• headers_to_remove
• query_parameters_to_set
• query_parameters_to_remove

If any of these are set we panic with an appropriate response.

We now (correctly) set headers sent to the upstream from the headers field.

Confirmed this locally by adding the following to the authconfig:

headers:
  "simple":
    json:
      properties:
        "data":
          value: true

Make the request:

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

See in the echo response of the upstream that it receives the header:

{
  "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": "10.244.0.18",
    "X-Forwarded-Proto": "http",
    "X-Envoy-Internal": "true",
    "X-Request-Id": "ebd0ab64-73c4-4a03-ad20-9ce810a3f057",
    "Simple": "{\"data\":true}",
    "X-Envoy-Expected-Rq-Timeout-Ms": "15000",
    "Version": "HTTP/1.1"
  },
  "uuid": "4a8906a8-31ec-493f-98a9-513ff7b4c79b"
}