Get basic file upload functionality working

app/Http/Controllers/Api/Client/Servers/DownloadBackupController.php

@@ -82,7 +82,7 @@ class DownloadBackupController extends ClientApiController
                 throw new BadRequestHttpException;
         }
 
-        return JsonResponse::create([
+        return new JsonResponse([
             'object' => 'signed_url',
             'attributes' => [
                 'url' => $url,

app/Http/Controllers/Api/Client/Servers/FileUploadController.php

@@ -0,0 +1,73 @@
+<?php
+
+namespace Pterodactyl\Http\Controllers\Api\Client\Servers;
+
+use Carbon\CarbonImmutable;
+use Pterodactyl\Models\User;
+use Pterodactyl\Models\Server;
+use Illuminate\Http\JsonResponse;
+use Pterodactyl\Services\Nodes\NodeJWTService;
+use Pterodactyl\Http\Controllers\Api\Client\ClientApiController;
+use Pterodactyl\Http\Requests\Api\Client\Servers\Files\UploadFileRequest;
+
+class FileUploadController extends ClientApiController
+{
+    /**
+     * @var \Pterodactyl\Services\Nodes\NodeJWTService
+     */
+    private $jwtService;
+
+    /**
+     * FileUploadController constructor.
+     *
+     * @param \Pterodactyl\Services\Nodes\NodeJWTService $jwtService
+     */
+    public function __construct(
+        NodeJWTService $jwtService
+    ) {
+        parent::__construct();
+
+        $this->jwtService = $jwtService;
+    }
+
+    /**
+     * Returns a url where files can be uploaded to.
+     *
+     * @param \Pterodactyl\Http\Requests\Api\Client\Servers\Files\UploadFileRequest $request
+     * @param \Pterodactyl\Models\Server $server
+     *
+     * @return \Illuminate\Http\JsonResponse
+     */
+    public function __invoke(UploadFileRequest $request, Server $server)
+    {
+        return new JsonResponse([
+            'object' => 'signed_url',
+            'attributes' => [
+                'url' => $this->getUploadUrl($server, $request->user()),
+            ],
+        ]);
+    }
+
+    /**
+     * Returns a url where files can be uploaded to.
+     *
+     * @param \Pterodactyl\Models\Server $server
+     * @param \Pterodactyl\Models\User $user
+     * @return string
+     */
+    protected function getUploadUrl(Server $server, User $user)
+    {
+        $token = $this->jwtService
+            ->setExpiresAt(CarbonImmutable::now()->addMinutes(15))
+            ->setClaims([
+                'server_uuid' => $server->uuid,
+            ])
+            ->handle($server->node, $user->id . $server->uuid);
+
+        return sprintf(
+            '%s/upload/file?token=%s',
+            $server->node->getConnectionAddress(),
+            $token->__toString()
+        );
+    }
+}

app/Http/Requests/Api/Client/Servers/Files/UploadFileRequest.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Pterodactyl\Http\Requests\Api\Client\Servers\Files;
+
+use Pterodactyl\Models\Permission;
+use Pterodactyl\Http\Requests\Api\Client\ClientApiRequest;
+
+class UploadFileRequest extends ClientApiRequest
+{
+    /**
+     * @return string
+     */
+    public function permission()
+    {
+        return Permission::ACTION_FILE_CREATE;
+    }
+}