Fix #2685 [BUG] S3 block spilling no longer passes request headers

[Trianz-Akshay]

Issue #, if available:
#2685

Description of changes:

This PR fixes issue #2685 where spill_put_request_headers configuration was incorrectly being set as object metadata instead of request headers on S3 PutObject requests. This caused SSE-KMS encryption headers to not appear in CloudTrail requestParameters, breaking encryption requirements and audit logging.

Problem

In versions >= v2024.42.1, the spill_put_request_headers environment variable values were being set as object metadata using .metadata() instead of request headers. This meant:

• SSE-KMS headers (x-amz-server-side-encryption, x-amz-server-side-encryption-aws-kms-key-id) were not sent as request parameters
• CloudTrail logs showed headers missing from requestParameters (they only appeared in responseElements)

Solution

Changed S3BlockSpiller.write() to use AwsRequestOverrideConfiguration to set headers as request headers via .overrideConfiguration() instead of .metadata().

Test Document:
Bug_Fix_2685.docx

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[amazon-inspector-n-virginia]

⏳ I'm reviewing this pull request for security vulnerabilities and code quality issues. I'll provide an update when I'm done

[amazon-inspector-n-virginia]

⏳ I'm reviewing this pull request for security vulnerabilities and code quality issues. I'll provide an update when I'm done

[amazon-inspector-n-virginia]

✅ I finished the code review, and didn't find any security or code quality issues.

[amazon-inspector-n-virginia]

✅ I finished the code review, and didn't find any security or code quality issues.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.35%. Comparing base (fe0a5d9) to head (bac649c).
⚠️ Report is 110 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3101      +/-   ##
============================================
+ Coverage     63.67%   68.35%   +4.68%     
- Complexity     4344     5009     +665     
============================================
  Files           621      636      +15     
  Lines         23286    24170     +884     
  Branches       2859     3000     +141     
============================================
+ Hits          14827    16522    +1695     
+ Misses         7070     6210     -860     
- Partials       1389     1438      +49     

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[AbdulR3hman]

return an optional here is better than nulls.

[Trianz-Akshay]

Thanks for the suggestion. Updated the code to return an Optional instead of null.