fix(source): skip PodIP-derived records when PodIP is empty

[immanuwell]

What does it do ?

Skips records that need PodIP while Kubernetes has not assigned one.
Explicit targets and node based records keep working

Motivation

Fixes #6375. Supersedes #6376

Repro:

1. Run ExternalDNS with the pod source and Azure Private DNS
2. Create a Pod with external-dns.kubernetes.io/internal-hostname, and keep it Pending with an unmatched node selector
3. Current master creates a CNAME with an empty target
4. When the Pod gets an IP, Azure rejects the A record because that CNAME already exists

Pretty easy to hit during autoscaling

More

• Yes, this PR title follows Conventional Commits
• Yes, I added unit tests
• No end user docs needed for this bug fix

[kubernetes-prow]

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[kubernetes-prow]

Hi @immanuwell. Thanks for your PR.

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[mloiseleur]

/ok-to-test

[mloiseleur]

@immanuwell Did you confirm the fix is working? Would you please share what you used and your findings?

[coveralls]

Coverage Report for CI Build 33536224558

Warning

Build has drifted: This PR's base is out of sync with its target branch, so coverage data may include unrelated changes.
Quick fix: rebase this PR. Learn more →

Coverage increased (+0.01%) to 81.599%

Details

• Coverage increased (+0.01%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 2 coverage regressions across 1 file.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

2 previously-covered lines in 1 file lost coverage.

File	Lines Losing Coverage	Coverage
pod.go	2	96.63%

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Coverage Stats

Relevant Lines:	18956
Covered Lines:	15468
Line Coverage:	81.6%
Coverage Strength:	1110.78 hits per line

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💛 - Coveralls