[FEATURE] Add option to enable image deletion from k3d managed registries

[sgaist]

Is your feature request related to a problem or a Pull Request

It's rather a limitation. Currently it's not possible to delete images from the registries created by k3d. While the endpoints are present the delete operation is disabled which is the default behaviour.

The goal of this flag is to allow administratosr to manage the content of the registry without having to recreate it.

I have a proof of concept working that I can submit.

Scope of your request

Do you need...

• a new flag for a command (e.g. k3d cluster create --<your-flag>)?
  • which command?

k3d registry create --delete-enabled

Describe the solution you'd like

The most simple solution would be a boolean flag which will be used to start the registry with the appropriate environment variable set. In this case REGISTRY_STORAGE_DELETE_ENABLED.

Describe alternatives you've considered

Another possible implementation would be to add an option, rather than a flag, allowing to set additional environment variables.
For example: k3d registry create --extra-env REGISTRY_STORAGE_DELETE_ENABLED=true would have in the end the same effect.