Integrate Prometheus Blackbox Exporter

blackbox-exporter is a dedicated services that monitors HTTP (or other) resources with regards to uptime, latency, status code and more.

It can be used to monitor our backplane services as well as custom defined endpoints.

• all endpoints of the space itself (portainer, grafana, prometheus, proxy.$APOLLO_SPACE_DOMAIN)
• custom https endpoints (APOLLO_APP_PROMETHEUS_BLACKBOX_CUSTOM_PROBES) - this can be used to monitor another apollo cluster for example