feat: support for topic in notification

using same topic twice will restore existing notification in that topic
if any. this can be useful if you want to remind users about some
specific thing over time

Signed-off-by: Heikki Hellgren <heikki.hellgren@op.fi>

plugins/notifications-node/src/service/DefaultNotificationService.ts

@@ -38,6 +38,7 @@ export type NotificationSendOptions = {
   title: string;
   description: string;
   link: string;
+  topic?: string;
 };
 
 /** @public */