Controller: emit lifecycle events when the VM gets restarted or deleted (#208)

* Controller: emit lifecycle events when the VM gets restarted or deleted

* vm_{scheduling,run}_time → vm_{scheduling,run}_duration for clarity

* Update VM endpoint: only update VM started time when zero

internal/controller/lifecycle/lifecycle.go

@@ -0,0 +1,34 @@
+package lifecycle
+
+import (
+	v1 "github.com/cirruslabs/orchard/pkg/resource/v1"
+	"go.uber.org/zap"
+	"time"
+)
+
+func Report(vm *v1.VM, message string, logger *zap.SugaredLogger) {
+	args := []interface{}{
+		"component", "lifecycle",
+		"vm_uid", vm.UID,
+		"vm_name", vm.Name,
+		"vm_restart_count", vm.RestartCount,
+		"vm_image", vm.Image,
+		"vm_status", vm.Status,
+	}
+
+	if vm.ScheduledAt.IsZero() {
+		// VM was never scheduled
+		args = append(args, "vm_scheduling_duration", time.Since(vm.CreatedAt))
+	} else {
+		args = append(args, "vm_scheduling_duration", vm.ScheduledAt.Sub(vm.CreatedAt))
+	}
+
+	if vm.StartedAt.IsZero() {
+		// VM was never started
+		args = append(args, "vm_run_duration", time.Duration(0))
+	} else {
+		args = append(args, "vm_run_duration", time.Since(vm.StartedAt))
+	}
+
+	logger.With(args...).Info(message)
+}