4.x Webserver doc and migration guide should explain server beforeStart and afterStop hooks

[tjquinno]

Environment Details

• Helidon Version: 4
• Helidon SE or Helidon MP
• JDK version:
• OS:
• Docker version (if applicable):

---

Problem Description

Neither the web server doc nor the migration guide explains how the 3.x WebServer.whenShutdown method has been functionally replaced by the ServerLifeCycle.afterStop method (also available via inheritance on Service and Handler).

The regular doc should at least briefly discuss beforeStart and afterStop and the migration guide should discuss how this 3.x construct in the SE QuickStart Main.startServer method

        webserver.forSingle(ws -> {
            System.out.println("WEB server is up! http://localhost:" + ws.port() + "/greet");
            ws.whenShutdown().thenRun(() -> System.out.println("WEB server is DOWN. Good bye!"));
        })
        .exceptionallyAccept(t -> {
            System.err.println("Startup failed: " + t.getMessage());
            t.printStackTrace(System.err);
        });

can be essentially replaced in 4.x by this in the QuickStart SE Main.main method (for announcing start-up - this code is in the example):

WebServer server = WebServer.builder()
                .config(config.get("server"))
                .routing(Main::routing)
                .build()
                .start();

        System.out.println("WEB server is up! http://localhost:" + server.port() + "/simple-greet");

and by this addition to Greeting.java (this snippet is not in the QuickStart example) for announcing shutdown:

@Override
    public void afterStop() {
        System.out.println("WEB server is DOWN. Good bye!");
    }

(Or, for symmetry, the start-up announcement could be done in a new GreetService beforeStart method instead of in Main.main although the semantics of beforeStart are not quite the same as logging a message after invoking WebServer#start.)