feat: add an event after server is listening

Author: djMax

src/express-app/app.ts

@@ -429,6 +429,7 @@ export async function listen<SLocals extends AnyServiceLocals = ServiceLocals<Co
   });
 
   await listenPromise;
+  await service.onListening?.(app, port);
   return server;
 }
 

src/types.ts

@@ -78,6 +78,8 @@ export interface Service<
 
   // Called after a server is created but before the server starts listening
   attachServer?: (app: ServiceExpress<SLocals>, server: Server) => void | Promise<void>;
+  // Called after the server is listening
+  onListening?: (app: ServiceExpress<SLocals>, port: number) => void | Promise<void>;
 
   start(app: ServiceExpress<SLocals>): void | Promise<void>;