fix: forward request headers when checking existing

[vincentsarago]

disclaimer: This PR was mostly done by Claude but I reviewed all the steps

I hit an issue when trying to create/update/delete collections (using PUT requests) where I got 502 errors 👇

re-running ingest_data.py against an already-seeded database hits a 502 Bad Gateway on the PUT (update) fallback. That's in the external stac-auth-proxy dependency, not this repo — Cql2ValidateTransactionMiddleware._fetch_existing (Cql2ValidateTransactionMiddleware.py:123-129) does an internal GET to fetch the existing record for update-validation but never forwards the caller's Authorization header, so it 401s against a private endpoint and that gets mapped to a 502. Worth a heads-up since your ingest script is idempotent-by-design (POST-then-PUT-on-409) and will hit this on every re-run

[claude]

Claude finished @vincentsarago's task in 2m 2s —— View job

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Claude's Task List

• Gather context (diff, files, CLAUDE.md)
• Review correctness / security
• Apply ponytail-review for over-engineering
• Post final review

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✅ No blocking issues — safe to merge.

The fix is correct and well-scoped: EnforceAuthMiddleware runs before Cql2ValidateTransactionMiddleware in the middleware stack (app.py — last-added-runs-first), so the caller is already authenticated by the time this middleware's internal _fetch_existing GET fires. Forwarding the caller's Authorization/Cookie headers to that internal call is therefore appropriate, not a privilege-escalation concern. The header-stripping list (host, content-length, content-type, transfer-encoding) correctly prevents the original bodied PUT/PATCH's Content-Length/Content-Type from leaking onto the bodyless internal GET, which the regression test (test_does_not_forward_incoming_content_length) confirms.

Non-blocking observations:

• Cql2ValidateTransactionMiddleware.py:25-27 — _forward_headers builds a dict via {k: v for k, v in headers.items() ...}. Starlette's Headers.items() can yield repeated keys for multi-valued headers (e.g. multiple Forwarded/X-Forwarded-For from an upstream proxy); the dict comprehension silently keeps only the last occurrence. Unlikely to matter for the Authorization/Cookie case this PR targets, so not blocking.
• Cql2ValidateTransactionMiddleware.py:133-139 — _fetch_existing's headers parameter is typed Optional[Headers] = None with a ... if headers else None fallback, but both call sites (_handle_update, _handle_delete) always pass a real Headers object now — the None path is unreachable in practice.

Simplify (ponytail)

• Cql2ValidateTransactionMiddleware.py:133-139 — drop the now-dead Optional[...] = None default and the if headers else None ternary on _fetch_existing; make headers: Headers required and pass it straight to _forward_headers, since every real caller already supplies it.

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💰 Estimated review cost: $0.75 · 2m01s · 21 turns