chore: Sort notifications based on last_activity_at.

app/finders/notification_finder.rb

@@ -60,6 +60,6 @@ class NotificationFinder
   end
 
   def notifications
-    @notifications.page(current_page).per(RESULTS_PER_PAGE).order(updated_at: :desc)
+    @notifications.page(current_page).per(RESULTS_PER_PAGE).order(last_activity_at: :asc)
   end
 end

app/models/notification.rb

@@ -49,7 +49,7 @@ class Notification < ApplicationRecord
 
   # TODO: Get rid of default scope
   # https://stackoverflow.com/a/1834250/939299
-  default_scope { order(id: :desc) }
+  default_scope { order(last_activity_at: :desc) }
 
   PRIMARY_ACTORS = ['Conversation'].freeze