feat: add gcp affinity annotation parsing

[chakravardhan]

What type of PR is this?
/kind feature

What this PR does / why we need it:

This PR introduces support for parsing Nginx Ingress session affinity annotations and translating them to GKE Gateway API resources.
Specifically, this PR:

• Adds parsing for nginx.ingress.kubernetes.io/affinity and nginx.ingress.kubernetes.io/session-cookie-max-age in the ingress-nginx provider.
• Automatically generates a GCPBackendPolicy with SessionAffinityConfig set to GENERATED_COOKIE when affinity: "cookie" is detected and the tool is run with --emitters=gce.
• Maps session-cookie-max-age to CookieTTLSec with strict bound-checking [0, 1209600] (14 days) to align with GCP's API constraints, surfacing validation errors early for invalid configurations.

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

Added support for translating Nginx Ingress annotations `affinity: "cookie"` and `session-cookie-max-age` into `GCPBackendPolicy` SessionAffinityConfigs when using the `gce` emitter.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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

Hi @chakravardhan. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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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[Stevenjin8]

I think I might havesaid this in another PR, but can we avoid using the ProviderSpecificServiceIR? Its only there for backcompat reasons. For example, what if another emitter also wants to implement sessionaffinity? Would they have to read ProviderSpecificServiceIR.Gce?

[chakravardhan]

Agreed @Stevenjin8, Should we move the SessionAffinity outside ProviderSpecificServiceIR into a common ServiceContext variable? wdyt?

[Stevenjin8]

/ok-to-test

[Stevenjin8]

Can we avoid having provider specific fields in the IR. The whole point is that it isn't provider specific

[k8s-ci-robot]

PR needs rebase.

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[k8s-ci-robot]

@chakravardhan: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-ingress2gateway-e2e	7233168	link	true	/test pull-ingress2gateway-e2e

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[DamianSawicki]

1. Thanks for taking care of it! Since 1.0 is now official, it would be great to get this merged asap.
2. It may be outside the scope of this particular PR, but nginx.ingress.kubernetes.io/session-cookie-name can be translated with GCP HTTP_COOKIE session affinity type instead of GENERATED_COOKIE. It requires using GCPTrafficDistributionPolicy instead of GCPBackendPolicy to configure session affinity (https://docs.cloud.google.com/kubernetes-engine/docs/how-to/configure-gateway-resources#expanded-session-affinity).

[DamianSawicki]

Thanks for taking care of it! Since 1.0 is now official, it would be great to get this merged asap.

Actually, is this still relevant or was it superseded by #394?

[chakravardhan]

Thanks for taking care of it! Since 1.0 is now official, it would be great to get this merged asap.

Actually, is this still relevant or was it superseded by #394?

Yes, the current PR is superseded by #394. Its not relevant anymore unless we pivot the PR to produce GCPTrafficDistributionPolicy. I'll close this PR for now.