For a CopyObject whose source carries versioning, the response must echo the exact source version copied via x-amz-copy-source-version-id (SDK CopySourceVersionId), kept distinct from the newly created destination x-amz-version-id. RustFS set the destination version_id but left copy_source_version_id unset, so AWS SDK clients could not prove which source version was copied — the same field UploadPartCopy already populates.
Populate CopyObjectOutput.copy_source_version_id from the version actually read from the source, gated on the source bucket carrying versioning (enabled or suspended) and rendering the null version as "null", mirroring the GET/HEAD convention. Add an e2e regression test that copies a non-latest source version and asserts the source-version header equals the requested version, the destination header is a distinct new version, the destination bytes/size match the copied version, and the source version remains present.
Fixes#4976
Zhengchao An
edfb3c134f