rack app is being re-initialised for every request

[DangerDawson]

This took me a while to track down, but when we switched over to using memcached based seasions using the dalli gem we noticed that we were leaking memcache connections:

The culprit was this bit of code: https://github.com/petergoldstein/dalli/blob/main/lib/rack/session/dalli.rb#L70

As Hanami was re-initalising the app on every single request:

https://github.com/hanami/hanami/blob/1.3.x/lib/hanami/middleware_stack.rb#L52

Because the call method on for the rack builder was calling to_app on every request:

https://github.com/rack/rack/blob/da03bfab6497ab05e9ed795f5d3c033e47927483/lib/rack/builder.rb#L276

I am not sure if this is the correct way to fix this? or it was intended that the rack app should be re-initalised on every request?

#1322

Also I am not sure if this is present in Hanami v2 either