[site-reviews] prevent users from reviewing their own posts

/**
 * @param bool|string $isValid
 * @param \GeminiLabs\SiteReviews\Request $request
 * @return bool|string
 */
add_filter('site-reviews/validate/custom', function ($isValid, $request) {
    if (!is_user_logged_in()) {
        return $isValid;
    }
    $postIds = $request->sanitize('assigned_posts', 'array-int');
    $userId = get_current_user_id();
    foreach ($postIds as $postId) {
        $postAuthorId = (int) (get_post($postId)->post_author ?? 0);
        if ($userId === $postAuthorId) {
            return 'You are not allowed to review your own post.';
        }
    }
    return $isValid;
}, 10, 2);