[FEATURE] Enable option to keep pull-through registry when deleting a cluster

[devantler]

Scope of your request

When I run k3d cluster delete cluster-name to remove a cluster it deletes all resources created for that cluster. It would be nice if there was a CLI option to make sure any pull-through registry is kept, as these have a lot of value to avoid rate limitswhen creating new clusters that pull the same images from Docker.

Describe the solution you'd like

Maybe something like this:

k3d cluster delete cluster-name --keep-registry docker-io

[devantler]

Nevermind, I was able to persist the volume by making it a named docker volume:

registries:
  create:
    name: docker-io
    proxy:
      remoteURL: https://registry-1.docker.io
    volumes:
      - local-docker-registry:/var/lib/registry
  config: |
    mirrors:
      "docker.io":
        endpoint:
          - http://docker-io:5000