Add an egress CIDR allowlist to the SSRF guard (closes #204) (#217)

cmd/webhooker/main.go

@@ -157,6 +157,10 @@ func newApp() *fx.App {
 			session.New,
 			handlers.New,
 			middleware.New,
+			// The one SSRF guard both target-creation validation
+			// and the delivery dialer consult, so they cannot
+			// disagree about a destination.
+			delivery.NewGuard,
 			delivery.New,
 			delivery.NewArchiveSweeper,
 			// Wire *delivery.Engine as delivery.Notifier so the