Add active blocks list api endpoint with empty response

app/controllers/api/user_blocks/active_lists_controller.rb

@@ -0,0 +1,13 @@
+module Api
+  module UserBlocks
+    class ActiveListsController < ApiController
+      before_action :authorize
+
+      authorize_resource :class => :active_user_blocks_list
+
+      before_action :set_request_formats
+
+      def show; end
+    end
+  end
+end