Add administrative webhooks (#18510)

* Add administrative webhooks

* Fix error when webhook is deleted before delivery worker runs

app/workers/trigger_webhook_worker.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class TriggerWebhookWorker
+  include Sidekiq::Worker
+
+  def perform(event, class_name, id)
+    object = class_name.constantize.find(id)
+    WebhookService.new.call(event, object)
+  rescue ActiveRecord::RecordNotFound
+    true
+  end
+end