[feat:gw-api] add support for ServiceExternalTrafficPolicyLocal

[shuqz]

Issue

Description

add support for ServiceExternalTrafficPolicyLocal when ExternalTrafficPolicy is defined in Service Spec for NLB. To have default value for Local case, it needs to satisfy:

1. targetType = Instance
2. externalTrafficPolicy = Local
3. load balancer type = NLB

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 (changed in kind:Service YAML file)
  • test case 1: set externalTrafficPolicy: Cluster -> no difference, this is the default case
  • test case 2: set externalTrafficPolicy: Local and not specify healthCheckNodePort -> random number(range 30000-32767) is chosen for health check node port and other default values are taken
  • test case 3: set externalTrafficPolicy: Local and specify healthCheckNodePort -> healthCheckNodePort is chosen for health check node port and other default values are taken
  • test case 4: set externalTrafficPolicy: Local and specify healthCheckNodePort and under Type:NodePort -> get error " spec.healthCheckNodePort: Invalid value: 30001: may only be set when type is 'LoadBalancer' and externalTrafficPolicy is 'Local'"
• [✅] 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 @shuqz. Thanks for your PR.

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[zac-nixon]

nit: isServiceExternalTrafficPolicyTypeLocal will never be true for application lb, so you can drop the nlb check.

[zac-nixon]

interesting pattern :)

[zac-nixon]

I was expecting this to as a new property in the TG config to fit the pattern of defining TG attributes in that CRD. But I think this is ok, and it's not a one-way door. We can add the TG prop at a later time.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: shuqz, zac-nixon

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[zac-nixon]

/ok-to-test
/lgtm
/approved