Fatal error: Uncaught Error: Interface "Flarum\Foundation\KnownError" not found in /opt/lampp/htdocs/forum/flarum/vendor/fof/oauth/src/Errors/AuthenticationException.php:18 Stack trace: #0 {main} thrown in /opt/lampp/htdocs/forum/flarum/vendor/fof/oauth/src/Errors/AuthenticationException.php on line 18