Add per-webhook event retention reaper (closes #63)

cmd/webhooker/main.go

@@ -34,6 +34,7 @@ func main() {
 			config.New,
 			database.New,
 			database.NewWebhookDBManager,
+			database.NewRetentionReaper,
 			healthcheck.New,
 			session.New,
 			handlers.New,
@@ -44,6 +45,13 @@ func main() {
 			func(e *delivery.Engine) delivery.Notifier { return e },
 			server.New,
 		),
-		fx.Invoke(func(*server.Server, *delivery.Engine) {}),
+		fx.Invoke(
+			func(
+				*server.Server,
+				*delivery.Engine,
+				*database.RetentionReaper,
+			) {
+			},
+		),
 	).Run()
 }