* Fix issue #6847: S3 chunked encoding includes headers in stored content
- Add hasTrailer flag to s3ChunkedReader to track trailer presence
- Update state transition logic to properly handle trailers in unsigned streaming
- Enhance parseChunkChecksum to handle multiple trailer lines
- Skip checksum verification for unsigned streaming uploads
- Add test case for mixed format handling (unsigned headers with signed chunks)
- Remove redundant CRLF reading in trailer processing
This fixes the issue where chunk-signature and x-amz headers were appearing
in stored file content when using chunked encoding with newer AWS SDKs.
* Fix checksum validation for unsigned streaming uploads
- Always validate checksum for data integrity regardless of signing
- Correct checksum value in test case
- Addresses PR review feedback about checksum verification
* Add warning log when multiple checksum headers found in trailer
- Log a warning when multiple valid checksum headers appear in trailers
- Uses last checksum header as suggested by CodeRabbit reviewer
- Improves debugging for edge cases with multiple checksum algorithms
* Improve trailer parsing robustness in parseChunkChecksum
- Remove redundant trimTrailingWhitespace call since readChunkLine already trims
- Use bytes.TrimSpace for both key and value to handle whitespace around colon separator
- Follows HTTP header specifications for optional whitespace around separators
- Addresses Gemini Code Assist review feedback
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