Add ris mirror metrics

cmd/ris-mirror/rismirror/metrics/ris_mirror_metrics.go

+package metrics
+
+import (
+	"net"
+
+	vrf_metrics "github.com/bio-routing/bio-rd/routingtable/vrf/metrics"
+)
+
+// RISMirrorMetrics contains per router BMP metrics
+type RISMirrorMetrics struct {
+	Routers []*RISMirrorRouterMetrics
+}
+
+// RISMirrorRouterMetrics contains a routers RIS mirror metrics
+type RISMirrorRouterMetrics struct {
+	// Routers IP Address
+	Address net.IP
+
+	// SysName of the monitored router
+	SysName string
+
+	// VRFMetrics represent per VRF metrics
+	VRFMetrics []*vrf_metrics.VRFMetrics
+}