Use middleware Rack::ContentLength

lib/diversipub/rack_app.rb

@@ -22,6 +22,7 @@ module Diversipub
     def builder
       @builder ||= Rack::Builder.new.tap do |builder|
         builder.use Rack::Head
+        builder.use Rack::ContentLength
         builder.use Rack::Static, **rack_static_kwargs
         builder.use Rack::Protection, except: %i[session_hijacking]
         builder.run rest