Organize backend into product executable and shared Go modules

backend/product/sessions/metrics/metrics.go

@@ -0,0 +1,35 @@
+package sessionmetrics
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+type Operation string
+
+const (
+	Validation    Operation = "validation"
+	CurrentLogout Operation = "current_logout"
+	AllLogout     Operation = "all_logout"
+)
+
+type Outcome string
+
+const (
+	Active          Outcome = "active"
+	Succeeded       Outcome = "succeeded"
+	AlreadyInactive Outcome = "already_inactive"
+	MissingIdentity Outcome = "missing_identity"
+	StorageError    Outcome = "storage_error"
+)
+
+var lifecycle = promauto.NewCounterVec(prometheus.CounterOpts{
+	Namespace: "sendico",
+	Subsystem: "auth",
+	Name:      "session_lifecycle_total",
+	Help:      "Session validation and logout outcomes.",
+}, []string{"operation", "outcome"})
+
+func Observe(operation Operation, outcome Outcome) {
+	lifecycle.WithLabelValues(string(operation), string(outcome)).Inc()
+}