DEV: adds event_reminder (27) and event_invitation (28) (#10473)

Note that these events are also added to the list of events sent to push notifications.

app/models/notification.rb

@@ -113,6 +113,8 @@ class Notification < ActiveRecord::Base
                         bookmark_reminder: 24,
                         reaction: 25,
                         votes_released: 26,
+                        event_reminder: 27,
+                        event_invitation: 28
                        )
   end