Docker easier configuration

[miton18]

For Docker application,

practitioner need to create a Git repository and put a dockerfile in it. while this is the standard way to build a clevercloud application.
Sometimes practitioner already have a build Docker image on the official / private registry.

We should be able to make something like:

resource "clevercloud_docker" "cont1" {
  deployment {
    repository = "docker://nginx:trixie-perl"
  }
}

which:

• create an in memory git repo
• write a dockerfile with "FROM the_image"
• commit and push it to clevercloud