This is spawned off from the findings in the https://phabricator.wikimedia.org/T284238 spike.
Upon receipt of a push notification, the iOS app will need to fetch the notifications API to determine which content to show.
There is an edge case where the user could receive a push notification yet not have any new notifications to display here. We will be unable to suppress the notification without switching to a highly unreliable silent push method of delivery. This task is to determine what the content of this "empty" notification should be and how it should act when tapped.
There is also a chance that our Notification Service extension, which is called to populate the push notification content and will be fetching from the notifications API to see what is new, could take too long to respond. Maybe the service is down or the user's connection is flaky at this point. We will need to define some fallback content for the notification in this case.