moodle-report_usergrades/settings.php

<?php
defined('MOODLE_INTERNAL') || die();

if ($hassiteconfig) { // Needs this condition or there is error on login page
    $ADMIN->add('reports', new admin_externalpage(
        'report_usergrades',
        get_string('pluginname', 'report_usergrades'),
        new moodle_url('/report/usergrades/index.php'),
        'report/usergrades:view'
    ));
}