feat: Support configure target-group-attributes for different service port #4326

[praddy26]

Issue

Fixes #1234

Description

This PR introduces the ability to configure target group attributes for specific ports in Network Load Balancers (NLB). Previously, target group attributes were applied uniformly across all ports in a service. With this change, users can now specify different attributes for different ports, providing more granular control over target group behavior.

Key changes:
• Added support for port-specific target group attributes using the format service.beta.kubernetes.io/aws-load-balancer-target-group-attributes.{port}
• Maintained backward compatibility with existing service.beta.kubernetes.io/aws-load-balancer-target-group-attributes annotation
• Port-specific attributes override the default attributes when specified
• Empty values in port-specific attributes don't override global values, allowing selective attribute inheritance

Example usage:

# Set deregistration delay globally to 60 seconds, with different values for ports 80 and 443
annotations:
  service.beta.kubernetes.io/aws-load-balancer-type: nlb
  # Global attributes for all target groups
  service.beta.kubernetes.io/aws-load-balancer-target-group-attributes: deregistration_delay.timeout_seconds=60
  # Port-specific attributes
  service.beta.kubernetes.io/aws-load-balancer-target-group-attributes.80: deregistration_delay.timeout_seconds=30
  service.beta.kubernetes.io/aws-load-balancer-target-group-attributes.443: deregistration_delay.timeout_seconds=120

# Example with empty values (inheriting from global attributes)
annotations:
  service.beta.kubernetes.io/aws-load-balancer-target-group-attributes: target.group-attr-1=80
  # Empty value will keep the global attribute value
  service.beta.kubernetes.io/aws-load-balancer-target-group-attributes.3306: target.group-attr-1=

Note: When a port-specific attribute has an empty value, it will not override the global attribute value. This allows you to selectively inherit global values while overriding others.

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

Hi @praddy26. Thanks for your PR.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: praddy26
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[shraddhabang]

/ok-to-test