MDL-44642 grading: Add session keepalive during advanced grading setup

grade/grading/form/guide/edit.php

@@ -57,6 +57,10 @@ if ($mform->is_cancelled()) {
     redirect($returnurl);
 }
 
+// Try to keep the session alive on this page as it may take some time
+// before significant interaction happens with the server.
+\core\session\manager::keepalive();
+
 echo $OUTPUT->header();
 $mform->display();
-echo $OUTPUT->footer();
+echo $OUTPUT->footer();