Migrate all Announcement fields

aleksis/core/migrations/0081_migrate_announcements.py

@@ -19,6 +19,8 @@ def migrate_announcements(apps, schema_editor):
             datetime_start=announcement.valid_from,
             datetime_end=announcement.valid_until,
             polymorphic_ctype_id = announcement_ctype.pk,
+            extended_data=announcement.extended_data,
+            managed_by_app_label=announcement.managed_by_app_label,
         )
 
         announcement.calendarevent_ptr_id = event.pk