v.3.21.0

Improvements:

1. [LUNA-7875] Added functionality for deleting folders, subfolders and files within folders. See delete folder and delete subfolders for details.

2. [LUNA-7877] Added functionality to copy folder objects. See folder objects for details

Bugs fixed:

1. [LUNA-7968] When creating a folder for an invalid bucket name a proper error was handled

Migration:

See a migration manual.