add checkout controller and refactoring cart controller

app/controllers/api/cart_controller.rb

@@ -2,6 +2,8 @@
 
 # API Controller for manage user's cart
 class API::CartController < API::ApiController
+  include API::OrderConcern
+
   before_action :current_order, except: %i[create]
   before_action :ensure_order, except: %i[create]
 
@@ -37,18 +39,6 @@ class API::CartController < API::ApiController
 
   private
 
-  def order_token
-    request.headers['X-Fablab-Order-Token'] || cart_params[:order_token]
-  end
-
-  def current_order
-    @current_order = Order.find_by(token: order_token)
-  end
-
-  def ensure_order
-    raise ActiveRecord::RecordNotFound if @current_order.nil?
-  end
-
   def orderable
     Product.find(cart_params[:orderable_id])
   end

app/controllers/api/checkout_controller.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+# API Controller for cart checkout
+class API::CheckoutController < API::ApiController
+  include ::API::OrderConcern
+end

app/controllers/concerns/api/order_concern.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+# Concern for CartController and CheckoutController
+module API::OrderConcern
+  private
+
+  def order_token
+    request.headers['X-Fablab-Order-Token'] || cart_params[:order_token]
+  end
+
+  def current_order
+    @current_order = Order.find_by(token: order_token)
+  end
+
+  def ensure_order
+    raise ActiveRecord::RecordNotFound if @current_order.nil?
+  end
+end