Add administrative webhooks (#18510)

* Add administrative webhooks

* Fix error when webhook is deleted before delivery worker runs

app/controllers/admin/webhooks/secrets_controller.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module Admin
+  class Webhooks::SecretsController < BaseController
+    before_action :set_webhook
+
+    def rotate
+      authorize @webhook, :rotate_secret?
+      @webhook.rotate_secret!
+      redirect_to admin_webhook_path(@webhook)
+    end
+
+    private
+
+    def set_webhook
+      @webhook = Webhook.find(params[:webhook_id])
+    end
+  end
+end