How to monitor targets external to the cluster using user workload prometheus

Issue

• the need to monitor, using "user workloads monitoring" stack, applications external to the cluster.

• IMPORTANT NOTE: this works fine and it's supported but it should be used in a limited way so as not to saturate internal prometheus instances with external targets metrics. Prometheus statefulset is consuming resources that are in relation with the cluster size.

• IMPORTANT NOTE: promethes in the cluster should not be used as target of a remote write.