Fatal error: Uncaught Error: Interface "Sabre\CalDAV\Backend\BackendInterface" not found in D:\xampp\htdocs\pimcore\my-project\vendor\sabre\dav\lib\CalDAV\Backend\SyncSupport.php:23 Stack trace: #0 {main} thrown in D:\xampp\htdocs\pimcore\my-project\vendor\sabre\dav\lib\CalDAV\Backend\SyncSupport.php on line 23