class ActionDispatch::MiddlewareStack::InstrumentationProxy

proxies the ‘call` method transparently and instruments the method call.
This class is used to instrument the execution of a single middleware. It

def call(env) 

def call(env)
  ActiveSupport::Notifications.instrument(EVENT_NAME, @payload) do
    @middleware.call(env)
  end
end

def initialize(middleware, class_name) 

def initialize(middleware, class_name)
  @middleware = middleware
  @payload = {
    middleware: class_name,
  }
end