This container can be pulled via:
  docker pull registry.opensuse.org/opensuse/leap/15.6/images/totest/containers/opensuse/leap-dnf:15.6
  docker pull registry.opensuse.org/opensuse/leap/15.6/images/totest/containers/opensuse/leap-dnf:15.6.5.598

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.