[site-reviews] Prevent self reviews

add_filter('site-reviews/validate/custom', function ($result, $request) {
    $userIds = explode(',', $request->assigned_users);
    $userIds = array_map('intval', $userIds);
    if (in_array(wp_get_current_user()->ID, $userIds)) {
        return 'You are not allowed to submit a review for yourself.';
    }
    return $result;
}, 10, 2);