[rage] Implement pipeline in routes

Rage allows routing to Rack directly for simple responses:
https://api.rage-rb.dev/Rage/Router/DSL/Handler#get-instance_method

Author: p8

frameworks/rage/app/controllers/benchmark_controller.rb

@@ -31,10 +31,6 @@ def self.dataset_items = @dataset_items
     headers["server"] = SERVER_NAME
   end
 
-  def pipeline
-    render plain: 'ok'
-  end
-
   def baseline_one
     total = params[:a].to_i + params[:b].to_i
     if request.post?

frameworks/rage/config/routes.rb

@@ -1,5 +1,9 @@
 Rage.routes.draw do
-  get  '/pipeline',    to: 'benchmark#pipeline'
+  get  '/pipeline', to: ->(env) do
+    [200, {
+      'content-type' => 'text/plain'
+    }, ['ok']]
+  end
   get  '/baseline11',  to: 'benchmark#baseline_one'
   post '/baseline11',  to: 'benchmark#baseline_one'
   get  '/baseline2',   to: 'benchmark#baseline_two'