This container can be pulled via:
  docker pull registry.opensuse.org/opensuse/alertmanager:0.30
  docker pull registry.opensuse.org/opensuse/alertmanager:0.30.0
  docker pull registry.opensuse.org/opensuse/alertmanager:0.30.0-36.137
  docker pull registry.opensuse.org/opensuse/alertmanager:latest

Set DOCKER_CONTENT_TRUST=1 to enable image tag verification.