Change AUTHORIZED_FETCH to not block unauthenticated REST API access (#19803)

New environment variable `DISALLOW_UNAUTHENTICATED_API_ACCESS`

app/controllers/api/base_controller.rb

@@ -133,7 +133,7 @@ class Api::BaseController < ApplicationController
   end
 
   def disallow_unauthenticated_api_access?
-    authorized_fetch_mode?
+    ENV['DISALLOW_UNAUTHENTICATED_API_ACCESS'] == 'true' || Rails.configuration.x.whitelist_mode
   end
 
   private