Validate partition mapper source keys before scheduling

[desusaiteja]

Reject non-canonical source partition keys before a partition mapper records downstream mapping for partitioned asset-triggered Dags. This keeps malformed-but-parseable keys from being normalized into incorrect target partitions, and adds regression coverage for temporal, allowed-key, product, chain, and scheduler paths.

closes: #58943

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Was generative AI tooling used to co-author this PR?

• Yes — Codex (GPT-5)

Generated-by: Codex (GPT-5) following the guidelines

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Important

🛠️ Maintainer triage note for @desusaiteja · by @potiuk · 2026-07-18 15:46 UTC

Helpful heads-up from the maintainers — please address before this PR can be reviewed:

• ❌ Provider tests. See docs.

See the Pull Request quality criteria for details.

The ball is in your court — you've been assigned to this PR. Fix the above, then mark it Ready for review.

_{Automated triage — may be imperfect; a maintainer takes the next look.}

[potiuk]

@desusaiteja — I've removed the ready for maintainer review label because the next step here is yours: this branch now has merge conflicts with main. It'll go back into the maintainer queue automatically once you rebase onto the latest main and push — no need to re-add the label by hand. There's no rush.

_{Automated triage note drafted by an AI-assisted tool — may get things wrong; a real Apache Airflow maintainer takes the next look once it's green. (why automated)}

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Drafted-by: Claude Code (Opus 4.8); reviewed by @potiuk before posting