Every campaign has an end.

Drop ahoy, because it's more trouble than it's worth. This means dropping
visits, campaigns, targets.

Campaigns are better run to analytics, such as:
* https://matomo.org/docs/tracking-campaigns/
* https://matomo.org/docs/tracking-goals-web-analytics/
* https://support.google.com/analytics/answer/1012040?hl=en

app/views/admin/versions/_object_desc_and_link.html.haml

@@ -74,10 +74,6 @@
   = link_to (current_or_last_object_state('Event', event_id).try(:title) || 'deleted event'),
           admin_conference_program_event_path(conference_short_title, event_id)
 
-- when 'Target'
-  target
-  = link_if_alive version, object.to_s, admin_conference_targets_path(conference_short_title), conference
-
 - when 'EventSchedule'
   event
   = link_to (current_or_last_object_state('Event', object.event_id).try(:title) || 'deleted'),
@@ -187,12 +183,6 @@
           admin_conference_ticket_path(conference_short_title, version.item_id),
           conference
 
-- when 'Campaign'
-  campaign
-  = link_if_alive version, object.name,
-          admin_conference_campaigns_path(conference_short_title),
-          conference
-
 - when 'DifficultyLevel'
   difficulty level
   = link_if_alive version, object.title,admin_conference_program_difficulty_levels_path(conference_short_title), conference