Set CORS headers for all .well-known responses

So we don't have to consider it for reverse proxies etc.

app/controllers/webfinger_controller.rb

@@ -1,8 +1,6 @@
-class WebfingerController < ApplicationController
+class WebfingerController < WellKnownController
   before_action :allow_cross_origin_requests, only: [:show]
 
-  layout false
-
   def show
     resource = params[:resource]
 
@@ -91,10 +89,4 @@ class WebfingerController < ApplicationController
       }
     }
   end
-
-  def allow_cross_origin_requests
-    return unless Rails.env.development?
-    headers['Access-Control-Allow-Origin'] = "*"
-    headers['Access-Control-Allow-Methods'] = "GET"
-  end
 end