Route53 weighted routing

[dominikhei]

Issue

#4747

Description

This PR adds support for Route53's Weighted routing policy for ACM DNS validation records, controlled by two new flags:

--route53-validation-record-routing-policy selects the routing policy (simple or weighted). simple preserves existing behavior exactly.
--route53-validation-record-weight the weight assigned to this controller's validation records. Only used when policy is weighted. Must be a positive integer (weight 0 would cause Route53 to never return the record, preventing ACM from completing validation).

When set to weighted, each controller creates its validation record using Route53's Weighted routing policy with --cluster-name as the SetIdentifier. This allows multiple controllers to each own a validation record for the same domain name without conflicting. Both flags are exposed as Helm values (route53ValidationRecordRoutingPolicy, route53ValidationRecordWeight) for users deploying via Helm.

I tested all changes end-to-end by creating two kubernetes clusters in EKS, each running its own AWS Load Balancer Controller deployment with --route53-validation-record-routing-policy=weighted and --cluster-name set to the respective cluster name. Both controllers were pointed at the same Route53 hosted zone and each processed an Ingress with create-acm-cert: "true" for the same hostname, triggering ACM certificate requests and DNS validation record creation. The Route53 output confirmed that both controllers successfully created coexisting weighted records for the same validation name.

With Simple routing policy this would fail, the second controller's ChangeResourceRecordSets call would be rejected because a record for that name already exists.

I additionally changed the following behavior:

The validation record create and delete paths now share a single buildValidationResourceRecordSet method to guarantee they stay in sync as Route53 requires a DELETE's ResourceRecordSet to exactly match what was originally created, including SetIdentifier and Weight for weighted records. I someone thinks this should not be the case, I am happy to roll this back :).

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 🌟

[kubernetes-prow]

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This pull-request has been approved by: dominikhei
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[kubernetes-prow]

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