Is your feature request related to a problem or challenge? Please describe what you are trying to do.
I'm trying to copy objects within a bucket as part of my data ingestion workflow. However, when thse objects exceed 5GB in size, this fails with an error. There's a built-in limit in the S3 API for the maximum size of a copy operation.

Describe the solution you'd like

I've outlined the solution i'd prefer in #561 - essentially the copy method should detect large copies and transparently switch to a multipart workflow.

Describe alternatives you've considered

Alternatively, we could also expose this API as part of the multipart-upload API.

Additional context