Accepted native handles of one image copy, returned by Images.copy/4.
mode is "pull", "push" or "relay". target is the destination's
operation: the image creation in pull and relay mode, the push token in push
mode. source is the source's operation: the download secret in pull mode
(nil for a public image), the export that drives a push, nil in relay mode.
aliases are the alias names Images.wait_copy/2 has yet to send once the
copy succeeds, where the pinned client creates them after its wait, and
fingerprint is the alias target known before the wait (relay). No field
performs I/O; the host cancels any handle with Operation.cancel/1.