Fatal error: Uncaught Error: Interface 'Sabre\DAV\Auth\Backend\BackendInterface' not found in /home/malert/WebDAV/vendor/sabre/dav/lib/DAV/Auth/Backend/AbstractDigest.php:21 Stack trace: #0 {main} thrown in /home/malert/WebDAV/vendor/sabre/dav/lib/DAV/Auth/Backend/AbstractDigest.php on line 21