Start a background task to copy several files/folders (also across libraries). Returns a task_id; query the progress with Query async operation progress, cancel with Cancel async operation. task_id is empty if the operation was completed immediately.

Requires copy permission on the source folder and read-write permission on the destination folder.

Since SecureCloud 13.0:

• Items whose name already exists in the destination get an automatically changed name (e.g. file (1).txt).
• If the destination library is encrypted and not unlocked for the user, 403 with body {"lib_need_decrypt": true} is returned.