Add administrative webhooks (#18510)

* Add administrative webhooks

* Fix error when webhook is deleted before delivery worker runs

config/routes.rb

@@ -235,6 +235,17 @@ Rails.application.routes.draw do
 
     resources :rules
 
+    resources :webhooks do
+      member do
+        post :enable
+        post :disable
+      end
+
+      resource :secret, only: [], controller: 'webhooks/secrets' do
+        post :rotate
+      end
+    end
+
     resources :reports, only: [:index, :show] do
       resources :actions, only: [:create], controller: 'reports/actions'