upgrades: add authorize.net integration.

Add integration for accepting payments with Authorize.net.

https://developer.authorize.net/hello_world.html

config/routes.rb

@@ -283,6 +283,7 @@ Rails.application.routes.draw do
   resources :user_name_change_requests, only: [:new, :create, :show, :index]
   resources :webhooks do
     post :receive, on: :collection
+    post :authorize_net, on: :collection
   end
   resources :wiki_pages, id: /.+?(?=\.json|\.xml|\.html)|.+/ do
     put :revert, on: :member