fix: stress that endpoint methods should be public

This is based on direct user feedback. Ppl do not immediately realise that non-public endpoint methods are not exposed to TypeScript.

Related: https://github.com/vaadin/flow/issues/7681

articles/fusion/application/fusion-application-accessing-backend.asciidoc

@@ -8,7 +8,7 @@ layout: page
 = Accessing Java Backend
 
 A server-side Java endpoint is a back-end method that is exposed for calling from client-side TypeScript code.
-An endpoint in Vaadin is a class that defines one or more API methods.
+An endpoint in Vaadin is a class that defines one or more public methods.
 
 Vaadin bridges Java backend endpoints and a TypeScript frontend. It generates
 TypeScript clients to call the Java backend in a type-checkable way.

articles/fusion/quick-start-tutorial.asciidoc

@@ -185,7 +185,7 @@ image::images/quickstart-running-1.png[Running project]
 ==  Create a Typed Server Endpoint
 
 One of the key features of Vaadin Fusion is type-safe server access through _endpoints_.
-When you define an `@Endpoint`, Vaadin creates the needed REST-like endpoints, secures them, and generates TypeScript interfaces for all the used data types and methods.
+When you define an `@Endpoint`, Vaadin creates the needed REST-like endpoints, secures them, and generates TypeScript interfaces for all the used data types and public methods.
 Having full-stack type safety helps you stay productive through autocomplete and helps guard against accidental UI breakage when the data model changes on the server.
 
 Create a new `TodoEndpoint.java` file in `src/main/java/com/example/application/data/endpoint`:
@@ -221,6 +221,7 @@ public class TodoEndpoint {
 }
 ----
 <1> Annotating a class with `@Endpoint` exposes it as a service for client-side views.
+All *public* methods of an endpoint are callable from TypeScript.
 <2> By default, endpoint access requires an authenticated user. `@AnonymousAllowed` enables access for anyone. See <<configuring-security,Configuring Security>> for more information on endpoint security.
 <3> Use Spring to autowire the `TodoRepository` for database access.