We did some work to get openapi / swagger metrics into Prometheus as part of T205870. With Alertmanager and alerts.git being a reality nowadays we should clean up the Icinga checks and move to Prometheus-based alerts.
While at it I think it'd be beneficial to at least brainstorm on the situation of modules/lvs/manifests/monitor_services.pp which is basically a separate list of openapi-based services, and IMHO it should be part of service::catalog instead.