* s3: implement Bucket Owner Enforced for object ownership
Objects uploaded by service accounts (or any user) are now owned by
the bucket owner when the bucket has BucketOwnerEnforced ownership
policy (the modern AWS default since April 2023).
This provides a more intuitive ownership model where users expect
objects created by their service accounts to be owned by themselves.
- Modified setObjectOwnerFromRequest to check bucket ObjectOwnership
- When BucketOwnerEnforced: use bucket owner's account ID
- When ObjectWriter: use uploader's account ID (backward compatible)
* s3: add nil check and fix ownership logic hole
- Add nil check for bucketRegistry before calling GetBucketMetadata
- Fix logic hole where objects could be created without owner when
BucketOwnerEnforced is set but bucket owner is nil
- Refactor to ensure objects always have an owner by falling back
to uploader when bucket owner is unavailable
- Improve logging to distinguish between different fallback scenarios
Addresses code review feedback from Gemini on PR #7913
* s3: add comprehensive tests for object ownership logic
Add unit tests for setObjectOwnerFromRequest covering:
- BucketOwnerEnforced: uses bucket owner
- ObjectWriter: uses uploader
- BucketOwnerPreferred: uses uploader
- Nil owner fallback scenarios
- Bucket metadata errors
- Nil bucketRegistry
- Empty account ID handling
All 8 test cases pass, verifying correct ownership assignment
in all scenarios including edge cases.
see https://blog.aqwari.net/xml-schema-go/
1. go get aqwari.net/xml/cmd/xsdgen
2. Add EncodingType element for ListBucketResult in AmazonS3.xsd
3. xsdgen -o s3api_xsd_generated.go -pkg s3api AmazonS3.xsd
4. Remove empty Grantee struct in s3api_xsd_generated.go
5. Remove xmlns: sed s'/http:\/\/s3.amazonaws.com\/doc\/2006-03-01\/\ //' s3api_xsd_generated.go
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