Split out markdown cache storage into a separate method

lib/banzai/renderer.rb

@@ -46,7 +46,7 @@ module Banzai
       return html if html.present?
 
       html = cacheless_render_field(object, field)
-      object.update_column(html_field, html) unless object.new_record? || object.destroyed?
+      update_object(object, html_field, html) unless object.new_record? || object.destroyed?
 
       html
     end
@@ -166,5 +166,9 @@ module Banzai
       return unless cache_key
       Rails.cache.send(:expanded_key, full_cache_key(cache_key, pipeline_name))
     end
+
+    def update_object(object, html_field, html)
+      object.update_column(html_field, html)
+    end
   end
 end