Encrypted docker with tomb

[jaromil]

Find an easy way to encrypt a docker that can run only when unlocked with a tomb key (tomb inside) and/or that unlocks a volume using tomb.

This should include creating a docker that is encrypted, a volume for dockers that is encrypted, and facilitating the open/close.

It can be either a tomb feature or a script in extras/

Reference discussion: https://www.reddit.com/r/docker/comments/hgqjlx/any_possible_way_to_encrypt_docker_volumes/