Fatal error: Uncaught Error: Interface "Http\Message\Authentication" not found in /var/www/html1/wp-content/plugins/zettle-pos-integration/modules/zettle-auth/src/OAuth/ZettleOAuthHeader.php:11 Stack trace: #0 {main} thrown in /var/www/html1/wp-content/plugins/zettle-pos-integration/modules/zettle-auth/src/OAuth/ZettleOAuthHeader.php on line 11