public function getEventTitle(array $event = []): string
    {
        $extra = [];

        if (!empty($event['calendar_attendees'])) {
            foreach ($event['calendar_attendees'] as $att) {
                if ($att instanceof EntityInterface) {
                    array_push($extra, $att->get('display_name'));
                }
            }
        }

        if (!empty($extra)) {
            $event['title'] .= ' - ' . implode("\n", $extra);
        }

        return $event['title'];
    }