Feature/Implement Rack middleware

lib/on_strum/healthcheck/rack_middleware.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+module OnStrum
+  module Healthcheck
+    class RackMiddleware
+      def initialize(app)
+        @app = app
+      end
+
+      def call(env)
+        request = build_request(env)
+        return [503, { 'Content-Type' => 'application/json' },[{ olo: :molo }.to_json]] if request.path.eql?('/healthcheck')
+
+        app.call(env)
+      end
+
+      private
+
+      attr_reader :app
+
+      def build_request(env)
+        ::Rack::Request.new(env)
+      end
+    end
+  end
+end