Support for Gateway API supported filters for HTTPRoutes

[sgayangi]

Description:
As specified in https://gateway-api.sigs.k8s.io/reference/spec/#gateway.networking.k8s.io/v1.HTTPRouteFilter, APK needs to be tested for the features it currently supports as well as what could potentially be supported as well.
This also needs to be added from the apk-conf level as well.

[sgayangi]

There are 5 filters in total:

• ExtensionRef
• HTTPURLRewriteFilter
• HTTPRequestMirrorFilter
• HTTPRequestRedirectFilter
• HTTPHeaderFilter

Of these 5,

• ExtensionRef
• HTTPURLRewriteFilter
• HTTPHeaderFilter (add, set and remove)
  are functional in APK.

The sample HTTPRoute filters used for testing HTTPHeaderFilter are given below:

1. requestHeaderModifier:

- type: "RequestHeaderModifier"
  requestHeaderModifier:
    add:
      - name: X-Request-Custom-Header
        value: "Request-Custom-Header"
    set:
      - name: User-Agent
        value: "Replaced existing value for user agent"
    remove: ["Postman-Token"]

2. responseHeaderModifier:

- type: "ResponseHeaderModifier"
  responseHeaderModifier:
    add:
      - name: X-Response-Custom-Header
        value: "Response-Custom-Header"
    set:
      - name: data
        value: "Replaced existing value for data from backend response"
    remove: ["access-control-allow-credentials"]

[sgayangi]

HTTPRequestMirrorFilter

• Mirrors requests to the backends specified under the filter
• Needs to be given a backendRef to mirror the request to
• The request is sent to the original backendRef provided under the rule as well
• However, the responses from the backend provided under the filter will be ignored; only the response from the original backend will be sent back to the client.

Sample:

- type: "RequestMirror"
  requestMirror:
    backendRef:
      group: "dp.wso2.com"
      kind: "Backend"
      name: "backend-736990a5eefb375887fdb20008ff04c43a8d3796-api"

https://www.envoyproxy.io/docs/envoy/latest/start/sandboxes/route-mirror

[sgayangi]

HTTPRequestRedirectFilter

• Redirects the request to the specified URL
• Cannot be used on the same rule as a URLRewrite
• Cannot have a backendRef in that match either

- type: "RequestRedirect"
  requestRedirect:
    scheme: "https"
    hostname: "webhook.site"
    path:
      type: "ReplaceFullPath"
      replaceFullPath: "/e961947c-0607-4d9d-9fe9-c7489cba84f8"
    port: 443
    statusCode: 301

[sgayangi]

Subtasks

• Add header modification and removal support to config deployer (PR: Add support for HeaderModifier filter in Config Deployer #2381)
• Add header modification and removal support to agent (Issue: Add header modifier, request redirect and request mirroring support in Agent #2387)
• Add header modification and removal policies to APIM with APK (PR: [APK] Update policies supported for APK product-apim#13498)
• Add request redirect and mirror filters to adapter (PR: Add support for RequestMirror and RequestRedirect filters #2391)
• Add request redirect and mirror filter support to config deployer (PR: Add request redirect and mirror filters functionality #2392)
• Add request redirect and mirror filter support to APIM APK Agent
• Add policies for request redirect and mirror filters to APIM (PR: [APK] Update policies supported for APK product-apim#13498)
• Update VSCode extension (PR: https://github.com/wso2-enterprise/vscode-extensions/pull/3287)

[sgayangi]

Fixed with PR #2392