Slug Driver Support (#2456)

- Support slug drivers for core's sluggable models, easily extends to other models
- Add automated testing for affected single-model API routes
- Fix nickname selection UI
- Serialize slugs as `slug` attribute
- Make min search length a constant

src/Api/Controller/ShowUserController.php

@@ -11,6 +11,8 @@ namespace Flarum\Api\Controller;
 
 use Flarum\Api\Serializer\CurrentUserSerializer;
 use Flarum\Api\Serializer\UserSerializer;
+use Flarum\Http\SlugManager;
+use Flarum\User\User;
 use Flarum\User\UserRepository;
 use Illuminate\Support\Arr;
 use Psr\Http\Message\ServerRequestInterface;
@@ -29,15 +31,22 @@ class ShowUserController extends AbstractShowController
     public $include = ['groups'];
 
     /**
-     * @var \Flarum\User\UserRepository
+     * @var SlugManager
+     */
+    protected $slugManager;
+
+    /**
+     * @var UserRepository
      */
     protected $users;
 
     /**
-     * @param \Flarum\User\UserRepository $users
+     * @param SlugManager $slugManager
+     * @param UserRepository $users
      */
-    public function __construct(UserRepository $users)
+    public function __construct(SlugManager $slugManager, UserRepository $users)
     {
+        $this->slugManager = $slugManager;
         $this->users = $users;
     }
 
@@ -47,17 +56,18 @@ class ShowUserController extends AbstractShowController
     protected function data(ServerRequestInterface $request, Document $document)
     {
         $id = Arr::get($request->getQueryParams(), 'id');
-
-        if (! is_numeric($id)) {
-            $id = $this->users->getIdForUsername($id);
-        }
-
         $actor = $request->getAttribute('actor');
 
-        if ($actor->id == $id) {
+        if (Arr::get($request->getQueryParams(), 'bySlug', false)) {
+            $user = $this->slugManager->forResource(User::class)->fromSlug($id, $actor);
+        } else {
+            $user = $this->users->findOrFail($id, $actor);
+        }
+
+        if ($actor->id === $user->id) {
             $this->serializer = CurrentUserSerializer::class;
         }
 
-        return $this->users->findOrFail($id, $actor);
+        return $user;
     }
 }