This container can be pulled via:
  docker pull registry.opensuse.org/devel/bci/sle-15-sp7/containerfile/suse/alertmanager:0.26
  docker pull registry.opensuse.org/devel/bci/sle-15-sp7/containerfile/suse/alertmanager:0.26.0
  docker pull registry.opensuse.org/devel/bci/sle-15-sp7/containerfile/suse/alertmanager:0.26.0-27.3

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.