define, build, and load docker container via nix?

runner.nix

virtualisation.oci-containers = {
    backend = "docker";
    containergs = {
      our-container-image = {
        autoStart = false;
        image = "our-container-image";
        imageFile = pkgs.dockerTools.buildImage {
          name = "our-container-image";
          contents = with pkgs; [ git git-lfs gitlab-runner ];
        };
      };
    };
  };