[feat] Remove machines that have been marked for deletion from the dns record

[tchinmai7]

What this PR does / why we need it:
When using a dns load-balancer i noticed traffic still arriving at the api-server on a node that was marked for deletion.

According to https://cluster-api.sigs.k8s.io/tasks/automated-machine-management/machine_deletions
the linodeMachine is deleted only after the nodes are drained. However, since the node's IP is still present in the dns record, new traffic was still sent to the node marked for deletion. To avoid this problem, this pr verifies that a CAPI machine exists, and isn't marked for deletion before adding that linodeMachine's IPs to the dns records.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

TODOs:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 10 lines in your changes missing coverage. Please review.

Project coverage is 62.80%. Comparing base (3c1acf8) to head (1d6eac1).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cloud/services/domains.go	66.66%	6 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #787      +/-   ##
==========================================
- Coverage   62.81%   62.80%   -0.02%     
==========================================
  Files          69       69              
  Lines        6721     6735      +14     
==========================================
+ Hits         4222     4230       +8     
- Misses       2258     2262       +4     
- Partials      241      243       +2     

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[Copilot]

Pull Request Overview

This PR refactors DNS entry generation to skip machines marked for deletion by their corresponding CAPI Machine, and updates tests to mock this behavior.

• Introduce processLinodeMachine to handle per-machine DNS option logic and skip deleted machines
• Refactor getDNSEntriesToEnsure to take a context, lock around mutation, and call the new helper
• Update tests to include OwnerReferences and add mockCAPIMachine helper for CAPI Machine mocking

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
cloud/services/domains.go	Refactored DNS entry computation and skipped deleted machines
cloud/services/domains_test.go	Added OwnerReferences in fixtures and new mockCAPIMachine

Comments suppressed due to low confidence (2)

cloud/services/domains.go:330

• Update the comment above getDNSEntriesToEnsure to reflect the new ctx parameter and that it now delegates to processLinodeMachine for each LinodeMachine, clarifying how d.options is populated.

func (d *DNSEntries) getDNSEntriesToEnsure(ctx context.Context, cscope *scope.ClusterScope) ([]DNSOptions, error) {

cloud/services/domains_test.go:384

• Add a test case for a LinodeMachine with no OwnerReferences (so GetOwnerMachine returns nil) to validate that the code handles missing owners without panicking.

		{name: "Skip - If a CAPI machine is deleted, don't add its IP to the Domain but include other machines",

[Copilot]

[nitpick] Distinguish between a missing owner (nil) and a deleted CAPI Machine—silently skipping on nil may hide misconfigured resources. Consider logging or returning an explicit error for missing owners.