feat: support secret for consumer.credential

[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:

apiVersion: v1
kind: Secret
metadata:
  name: key-auth-secret
data:
  key: c2FtcGxlLWtleQ==
---
apiVersion: v1
kind: Secret
metadata:
  name: basic-auth-secret
data:
  username: c2FtcGxlLXVzZXI=
  password: c2FtcGxlLXBhc3N3b3Jk
---
apiVersion: gateway.apisix.io/v1alpha1
kind: Consumer
metadata:
  name: consumer-sample
spec:
  gatewayRef:
    name: api7ee
  credentials:
    - type: basic-auth
      name: basic-auth-sample
      secretRef:
        name: basic-auth-secret
    - type: key-auth
      name: key-auth-sample
      secretRef:
        name: key-auth-secret
    - type: key-auth
      name: key-auth-sample2
      config:
        key: sample-key2

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

[Copilot]

Pull Request Overview

This PR adds support for secrets in consumer credentials, updating both test cases and core logic to accommodate secret-based authentication configuration.

• Updated e2e tests to use the new credentials and secretRef for basic-auth and key-auth.
• Modified the translator to convert secret values from []byte to string.
• Added secret indexer logic and updated consumer controller to watch and reconcile secrets.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
test/e2e/crds/consumer.go	Updated test cases to support secret-based credentials.
internal/provider/adc/translator/consumer.go	Ensured secret data is converted to strings correctly.
internal/controller/indexer/indexer.go	Added secret indexing for consumers.
internal/controller/consumer_controller.go	Updated controller to watch secrets and adjusted key ordering.

[github-actions]

conformance test report

apiVersion: gateway.networking.k8s.io/v1
date: "2025-04-07T00:23:36Z"
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
    - HTTPRoutePathMatchOrder
    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: 2
      Passed: 9
      Skipped: 22
  name: GATEWAY-HTTP
  summary: Core tests failed with 2 test failures.

[ronething]

lgtm