docs: document MenuConfiguration (vaadin#3770)

* docs: document MenuConfiguration

Renamed menu-registry to menu-configuration. Updated content to match with new simpler public API of MenuConfiguration. MenuRegistry was changed to internal API and only new public API is documented.

RelatedTo: vaadin/flow#20063

* Updated by review comments

* First pass at editing new document.

* Second pass at editing.

* A few more minor edits.

---------

Co-authored-by: Russell J.T. Dyer <6652767+russelljtdyer@users.noreply.github.com>

Author: tltv

articles/flow/advanced/menu-configuration.adoc

@@ -0,0 +1,49 @@
+---
+title: Menu Configuration
+description: Collecting menu annotated routes for menu generation.
+order: 115
+---
+
+
+= Menu Configuration
+
+To generate a custom menu, the [classname]`MenuConfiguration` may be used for collecting defined server and client routes. Client routes are taken from the FileSystem routes definition. Server routes come from routes annotated with [annotationname]`@Menu`.
+
+The collected menu items are filtered by access control from the [classname]`UI` (i.e., [classname]`NavigationAccessControl` and [classname]`ViewAccessChecker`). If the application has login and route defined `Roles`, the returned list is filtered on only available routes.
+
+
+== Creating Routes Menu
+
+For a Flow application, any route annotated with [annotationname]`@Menu` is eligible for collection.
+
+To get the available menu routes, call the static method `MenuConfiguration.getMenuEntries()`. This returns a [classname]`List<MenuEntry>`, first sorted in order found, then by path alphabetically and locale. It makes creating a simple menu by using [classname]`Anchor`, which can look like this:
+
+[source,java]
+----
+List<MenuEntry> menuEntries = MenuConfiguration.getMenuEntries();
+menuEntries.forEach(entry -> layout.add(new Anchor(entry.path(), entry.title())));
+----
+
+
+== Data Returned for Menu Entries
+
+The [classname]`MenuEntry` for a route contains information on the route. Using this data, it's possible to populate a menu, automatically.
+
+The data contained is as follows:
+
+`path`::
+Route path that should be used for navigation.
+
+`title`::
+Title set in the [annotationname]`@Menu` annotation or the [annotationname]`@PageTitle`, if defined -- otherwise, the class simple name. For the client, title is populated from the FS router data.
+
+`order`::
+Order number for the menu entry, if defined.
+
+`icon`::
+Icon to use in the menu. This value can be entered inside a `<vaadin-icon>` element's `icon` attribute. It accepts icon group and a name like `vaadin:file`. Or the value can be given in `<vaadin-icon>` element's `src` attribute, which takes the path to the icon (e.g., `line-awesome/svg/lock-open-solid.svg`).
+
+`menuClass`::
+Source class of the [annotationname]`@Menu` annotation. Always null for client routes.
+
+[discussion-id]`647922A8-D542-4FA7-AAF6-44D40FC6A33B`

articles/flow/advanced/menu-registry.adoc

@@ -238,7 +238,7 @@ public class MainView extends Div implements RouterLayout {
 
 For more information on `RouterLayout`, see <<../routing/layout.adoc#,Router Layouts & Nested Router Targets>>.
 
-Information on dynamic menu item generation, see <<../advanced/menu-registry#,Menu Registry>>.
+Information on dynamic menu item generation, see <<../advanced/menu-configuration#,Menu Configuration>>.
 
 [NOTE]
 If the application is using access protection add [annotationname]`@AnonymousAllowed` on the `MainView` so that the request is not denied.