API: Include User Metadata in GetObject

[nopcoder]

Currently, the GetObject operation doesn't include user metadata alongside the object content.
This would be a valuable addition. Similar to the StatObject operation, we should provide user metadata as an optional part of the response.

This would allow clients to easily access relevant user information alongside the object data without another call.

Suggested Action: by request, include the user metadata on the response headers to GetObject.