Support Object Composition

[tustvold]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

Various stores have facilities for object composition:

• https://docs.aws.amazon.com/AmazonS3/latest/API/API_UploadPartCopy.html
• https://cloud.google.com/storage/docs/xml-api/put-object-compose
• https://learn.microsoft.com/en-us/rest/api/storageservices/put-block-from-url

Describe the solution you'd like

Not sure, but documenting that this is something supported by the stores but not the ObjectStore trait

Describe alternatives you've considered

Additional context

[tustvold]

One potential use-case for this is copying objects larger than the 5GB limit of CopyObject