Prometheus endpoint ?

[hotplug]

#1669 was merged some times ago but I don't see any reference to metrics in documentation.
Based on source code, i've tried to use MetricsAddr : "9000"

certificates/authority/config/config.go

Line 86 in 28a12e3

MetricsAddr string `json:"metricsAddr,omitempty"`

but this has no effect.