chore: more upgrade docs

Author: SychO9

docs/extend/routes.md

@@ -143,10 +143,6 @@ class HelloWorldController implements RequestHandlerInterface
 }
 ```
 
-### API Controllers
-
-The `Flarum\Api\Controller` namespace contains a number of abstract controller classes that you can extend to easily implement new JSON-API resources. See [Working with Data](api.md) for more information.
-
 ## Frontend Routes
 
 Adding routes to the frontend actually requires you to register them on _both_ the frontend and the backend. This is because when your route is visited, the backend needs to know to serve up the frontend, and the frontend needs to know what to display on the page.

docs/extend/update-2_0.md

@@ -61,10 +61,16 @@ Familiarize yourself with the new [Code Splitting](./code-splitting) feature to
 
 :::
 
-### Admin Search
+### Forum Search
 
 ##### <span class="breaking">Breaking</span>
-* `app.extensionData` has been renamed to `app.registry`, but you should now use the [`Admin` extender](./admin.md) instead.
+* The forum search UI has been refactored to use a new `SearchModal` component.
+* The `flarum/forum/components/Search` component is no longer the global search component, it can still be used for custom search purposes.
+* Custom global search sources should be registered in `flarum/forum/components/GlobalSearch` `sourceItems` method.
+* Custom global search sources should now implement the `GlobalSearchSource` interface instead of `SearchSource`, see https://github.com/flarum/framework/blob/2.x/framework/core/js/src/common/components/AbstractSearch.tsx#L26-L69.
+* The `flarum/forum/states/SearchState` class has been moved to `flarum/common/states/SearchState`.
+
+### Admin Search
 
 ##### <span class="notable">Notable</span>
 * The admin dashboard now has a search feature, as long as you register your settings/permissions using the `Admin` extender, then they will be automatically picked up.
@@ -97,6 +103,7 @@ Familiarize yourself with the new [Code Splitting](./code-splitting) feature to
 There have been many changes to the core frontend codebase, including renamed or moved methods/components, new methods/components, and more. It might help to look directly at the [JavaScript diffs](https://github.com/flarum/framework/issues?q=is%3Amerged+label%3Ajavascript+milestone%3A2.0+) to see what has changed. But here are some notable changes.
 
 ##### <span class="breaking">Breaking</span>
+* `app.extensionData` has been renamed to `app.registry`, but you should now use the [`Admin` extender](./admin.md) instead.
 * Some extension initializers [have been renamed to be more uniform](https://github.com/flarum/framework/pull/4003/files), if you are checking for initializer existence with `app.initializers.has('...')` you should update the name accordingly.
 * `IndexPage.prototype.sidebar` has been removed, use the `IndexSidebar` component instead.
 * `IndexPage.prototype.navItems` has been moved to `IndexSidebar.prototype.navItems`.