This container can be pulled via:
  docker pull registry.opensuse.org/home/dirkmueller/bci/cr/sle-15-sp6/containerfile/suse/rmt-nginx:1.21
  docker pull registry.opensuse.org/home/dirkmueller/bci/cr/sle-15-sp6/containerfile/suse/rmt-nginx:1.21-1.140

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.