Fix handling of upload IDs on backups

app/Models/Backup.php

@@ -68,6 +68,11 @@ class Backup extends Model
         'upload_id' => null,
     ];
 
+    /**
+     * @var string[]
+     */
+    protected $guarded = ['id', 'created_at', 'updated_at', 'deleted_at'];
+
     /**
      * @var array
      */
@@ -80,7 +85,7 @@ class Backup extends Model
         'disk' => 'required|string',
         'checksum' => 'nullable|string',
         'bytes' => 'numeric',
-        'upload_id' => 'nullable|uuid',
+        'upload_id' => 'nullable|string',
     ];
 
     /**