feat: add support for internal service specific labels

[samuelarogbonlo]

Add support for internal service specific labels
Fixes #12428

Description
This PR adds the ability to specify labels specifically for the internal ingress-nginx service without affecting the main controller service. This is particularly useful for use cases like external-dns configuration where labels need to be set only on the internal service.

Changes

• Modified templates/controller-service-internal.yaml to support internal-specific labels
• Removed mandatory annotations requirement for internal service
• Fixed indentation in templates/controller-deployment.yaml
• Added test case for internal service labels

Code Changes

1. Added support for internal-specific labels:

 labels:
    {{- include "ingress-nginx.labels" . | nindent 4 }}
    app.kubernetes.io/component: controller
  {{- if .Values.controller.service.internal.labels }}
    {{- toYaml .Values.controller.service.internal.labels | nindent 4 }}
  {{- end }}

2. Removed mandatory annotations requirement:

From

{{- if and .Values.controller.service.enabled .Values.controller.service.internal.enabled .Values.controller.service.internal.annotations -}}

To

{{- if and .Values.controller.service.enabled .Values.controller.service.internal.enabled -}}

Testing Performed
Tested the following scenarios:

1. Adding custom labels to internal service only
2. Verifying label isolation (labels on internal service don't appear on main service)
3. Creating internal service without requiring annotations
4. Confirming template renders correctly

Test configuration added in:
charts/ingress-nginx/ci/controller-service-internal-labels-values.yaml

Usage Example

controller:
  service:
    internal:
      enabled: true
      labels:
        external-dns.alpha.kubernetes.io/hostname: internal.example.com
        custom-label: test-value

Backward Compatibility
This change maintains backward compatibility by:

• Not changing behavior for existing configurations
• Only removing restrictions (required annotations)
• Preserving all existing label inheritance where appropriate
• Not requiring configuration of internal labels

Checklist

• [ ✅ ] Code follows repository style and conventions
• [ ✅ ] Templates render correctly
• [ ✅ ] Added test configuration
• [ ✅ ] Maintains backward compatibility
• [ ✅ ] Verified label isolation works as expected

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[k8s-ci-robot]

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This pull-request has been approved by: samuelarogbonlo
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[k8s-ci-robot]

Hi @samuelarogbonlo. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[Gacko]

/hold

[Gacko]

Looks better! Thank you! Please also consider adding unit tests in the tests/ directory.

[Gacko]

I guess something went wrong here, right?

[Gacko]

Looks better! Could you now also add such a field to the external service?

[Gacko]

Suggested change