feat: support proxy external service

[AlinsRan]

Type of change:

• Bugfix
• New feature provided
• Improve performance
• Backport patches
• Documentation
• Refactor
• Chore
• CI/CD or Tests

What this PR does / why we need it:

support service with ExternalName

apiVersion: v1
kind: Service
metadata:
  name: httpbin2
spec:
  type: ExternalName
  externalName: httpbin.org

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[github-actions]

conformance test report

apiVersion: gateway.networking.k8s.io/v1
date: "2025-04-22T10:11:55Z"
gatewayAPIChannel: standard
gatewayAPIVersion: v1.2.0
implementation:
  contact: null
  organization: API7
  project: api7-ingress-controller
  url: https://github.com/api7/api7-ingress-controller.git
  version: v2.0.0
kind: ConformanceReport
mode: default
profiles:
- core:
    failedTests:
    - HTTPRouteCrossNamespace
    result: failure
    skippedTests:
    - GatewayInvalidTLSConfiguration
    - GatewaySecretInvalidReferenceGrant
    - GatewaySecretMissingReferenceGrant
    - GatewaySecretReferenceGrantAllInNamespace
    - GatewaySecretReferenceGrantSpecific
    - HTTPRouteExactPathMatching
    - HTTPRouteHTTPSListener
    - HTTPRouteHeaderMatching
    - HTTPRouteHostnameIntersection
    - HTTPRouteInvalidBackendRefUnknownKind
    - HTTPRouteInvalidCrossNamespaceBackendRef
    - HTTPRouteInvalidCrossNamespaceParentRef
    - HTTPRouteInvalidNonExistentBackendRef
    - HTTPRouteInvalidParentRefNotMatchingSectionName
    - HTTPRouteInvalidReferenceGrant
    - HTTPRouteListenerHostnameMatching
    - HTTPRouteMatching
    - HTTPRouteMatchingAcrossRoutes
    - HTTPRoutePartiallyInvalidViaInvalidReferenceGrant
    - HTTPRouteReferenceGrant
    - HTTPRouteRequestHeaderModifier
    - HTTPRouteWeight
    statistics:
      Failed: 1
      Passed: 10
      Skipped: 22
  name: GATEWAY-HTTP
  summary: Core tests failed with 1 test failures.

[Copilot]

Pull Request Overview

This PR adds support for proxying ExternalName services. Key changes include:

• Adding end-to-end tests for ExternalName service support in both Ingress and HTTPRoute resources.
• Updating the ADC translator logic in both ingress and httproute to properly handle ExternalName services.
• Adjusting controller logic to detect and process ExternalName service types appropriately.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/e2e/ingress/ingress.go	Added tests for proxying ExternalName service in Ingress.
test/e2e/gatewayapi/httproute.go	Added tests for HTTPRoute ExternalName service proxy support.
internal/provider/adc/translator/ingress.go	Augmented translation for ExternalName services in Ingress.
internal/provider/adc/translator/httproute.go	Incorporated ExternalName service logic for HTTPRoute.
internal/controller/ingress_controller.go	Adjusted backend service processing for ExternalName service.
internal/controller/httproute_controller.go	Updated HTTPRoute backend reference processing for ExternalName.

Comments suppressed due to low confidence (1)

test/e2e/ingress/ingress.go:219

• [nitpick] Duplicate log statement 'By("create GatewayProxy")' appears in the test. Consider removing or updating the redundant message to improve test output clarity.

By("create GatewayProxy")

[ronething]

lgtm.