This container can be pulled via:
  docker pull registry.opensuse.org/opensuse/factory/zsystems/totest/containers/opensuse/squid:6.10
  docker pull registry.opensuse.org/opensuse/factory/zsystems/totest/containers/opensuse/squid:6.10-5.39
  docker pull registry.opensuse.org/opensuse/factory/zsystems/totest/containers/opensuse/squid:latest

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.