adds user-billing

[bwalsh]

Propagate requester billing project to Terra DRS Hub

Description

• Enable requester-pays GCS downloads through Terra DRS Hub by reading GOOGLE_PROJECT for each resolution request and sending its trimmed, non-empty value as userProject. The returned signed access URL is used unchanged, preserving its billing parameter and signature.

• Document the configuration and extend resolver and integration coverage for billing-project propagation, omission of empty values, signed-URL integrity, and successful downloads. Also update the Docker Syfon E2E test to verify unknown-checksum add-url objects can be pulled, and make Syfon test-process shutdown detection more reliable.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-14T22:47:05.754982Z	93e5607	PR opened

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[bwalsh]

Failure analysis

What was failing

The Syfon Docker E2E (add-url) job failed when pulling an object created with git drs add-url without a known SHA-256. The push registered its metadata, but the subsequent pull could not find a DRS record for the placeholder OID.

Why it failed

The placeholder OID is 64 hexadecimal characters, so Syfon treated it as a SHA-256 lookup. But the record stores it as a git-drs-placeholder checksum, not a real SHA-256. The normal SHA-256 lookup therefore returned no match.

How it was fixed

Placeholder records now use a non-SHA-shaped checksum value (git-drs-placeholder/), keeping synthetic OIDs out of Syfon’s SHA-256 index. When a normal checksum lookup misses, git-drs retries with that placeholder key. The lookup also continues to recognize records using the previous raw-OID representation.
For requester-pays downloads, GOOGLE_PROJECT is sent to Terra DRS Hub as userProject; the returned signed URL is preserved unchanged.

Validation

All three Docker E2E tests passed against the exact Syfon commit pinned by CI, including TestGitDrsDockerAddURLE2E.
go test ./internal/drsobject ./internal/lookup ./internal/transfer passed.

why did the changes made to support requestor pays cause these errors?

The requester-pays code did not cause the lookup failure. The failure came from a separate change in the same branch: the add-url E2E test was changed from expecting an unknown-checksum placeholder pull to fail to expecting it to succeed.
That pull already couldn’t resolve the placeholder: its OID is 64 hex characters, so git-drs queried Syfon as if it were a SHA-256. But the record stored it as a git-drs-placeholder checksum, which Syfon’s SHA-256 lookup doesn’t match. The new test expectation exposed that existing mismatch; it wasn’t a regression from sending userProject.
The fix stores placeholder checksums under a non-SHA-shaped key and retries missed lookups using that key. The incidental git config --global messages in the test log were diagnostic snapshots, not the cause.