Preserve source object metadata during multipart copy

[S-Saranya1]

Motivation and Context

When the multipart-enabled S3 client copies an object, it uses CreateMultipartUpload + UploadPartCopy instead of a single CopyObject call. Unlike CopyObject, CreateMultipartUpload has no MetadataDirective support, so when a customer explicitly set MetadataDirective.COPY, the directive was silently ignored and source object metadata was dropped on the destination.

Modifications

• Pass HeadObjectResponse (already retrieved for content-length) into copyInParts()
• When MetadataDirective is explicitly set to COPY, forward source metadata fields from the HeadObjectResponse to the CreateMultipartUploadRequest: metadata, contentType, cacheControl, contentDisposition, contentEncoding, contentLanguage, expires
• When MetadataDirective is REPLACE, behavior is unchanged — customer-provided values on CopyObjectRequest are used as before
• Updated S3TransferManager.copy() Javadoc to document that source metadata is preserved when MetadataDirective is set to COPY

Testing

• Added parameterized test multiPartCopy_metadataDirectiveCopyOrUnset_shouldForwardSourceMetadata — verifies all metadata fields from HeadObject are forwarded to CreateMultipartUpload when MetadataDirective is COPY
• Added multiPartCopy_metadataDirectiveReplace_shouldNotForwardSourceMetadata — verifies customer-provided metadata is used when MetadataDirective is REPLACE
• Added multiPartCopy_metadataDirectiveCopyWithCustomerMetadata_sourceMetadataShouldWin — verifies source metadata takes precedence when MetadataDirective is COPY, matching S3 CopyObject API behavior
• All existing CopyObjectHelper tests continue to pass

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license

[S-Saranya1]

Should we check == COPY instead? What if there's a new enum added in the future where metadata is not supposed to be passed

• Updated to COPY

Should we add all common fields of CreateMultipartUploadRequest and headObjectResponse? This way, we don't risk missing new fields

• HeadObjectResponse and CreateMultipartUploadRequest share fields (e.g. ServerSideEncryption, SSEKMSKeyId, StorageClass) that are already set from the customer's CopyObjectRequest via setSdkFields, overwriting those from HeadObject would be changing during copy. An explicit allow list should be good I guess. This matches what PHP and CLI forward.

[zoewangg]

Can we update javadoc to mention this copy metadata by default behavior?

[zoewangg]

Can we update javadoc to mention this copy metadata by default behavior?

[zoewangg]

Can we make this paramaterized test and add a test case metadataDirective set to COPY?

[S-Saranya1]

Done

[github-actions]

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