fix(minio): copy_object source string lets a key choose the version #457

Problem: CopySource=f'{bucket}/{key}': a key k?versionId=abc is parsed as a version (reproduced); client.copy_object fails above 5 GB.

Fix: Use the dict form {'Bucket':..,'Key':..} and client.copy (managed multipart).

Checklist

• fix with regression test
• docs updated where affected