get https://api.onesignal.com/notifications?app_id=&limit=&offset=&kind=&template_id=
View the details for a collection of messages.
Refer to View notification response for details on responses from this API.
Notification deletions
Messages sent through the API and Automated Messages are only accessible 30 days after creation; however, messages sent using the OneSignal dashboard are accessible for the app's lifetime.