Make server listing and single server view API endpoints work

app/Transformers/Api/Application/UserTransformer.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace Pterodactyl\Transformers\Api\Application;
+
+use Pterodactyl\Models\User;
+use Pterodactyl\Services\Acl\Api\AdminAcl;
+
+class UserTransformer extends BaseTransformer
+{
+    /**
+     * List of resources that can be included.
+     *
+     * @var array
+     */
+    protected $availableIncludes = ['servers'];
+
+    /**
+     * Return a generic transformed subuser array.
+     *
+     * @param \Pterodactyl\Models\User $user
+     * @return array
+     */
+    public function transform(User $user): array
+    {
+        return $user->toArray();
+    }
+
+    /**
+     * Return the servers associated with this user.
+     *
+     * @param \Pterodactyl\Models\User $user
+     * @return \League\Fractal\Resource\Collection|\League\Fractal\Resource\NullResource
+     */
+    public function includeServers(User $user)
+    {
+        if (! $this->authorize(AdminAcl::RESOURCE_SERVERS)) {
+            return $this->null();
+        }
+
+        $user->loadMissing('servers');
+
+        return $this->collection($user->getRelation('servers'), $this->makeTransformer(ServerTransformer::class), 'server');
+    }
+}