Set up basic monitoring for backend cluster

The plan is to set up monitoring using the kube-prometheus-stack helm chart: https://github.com/prometheus-community/helm-charts/tree/main/charts/kube-prometheus-stack But according to some sources (e.g. https://github.com/prometheus-community/helm-charts/issues/2865) it might be neccessary to adapt the configuration in order to not have duplicate data.