Namespace routes to our controllers

For the transition process between the two promotion systems, we want
the admins to still have access to the legacy promotions. Prior to this
commit, this access was thwarted as we used the exact same paths as core
Solidus. This adds an extra `friendly/` to the path, so that the paths
can be distinguished. This in turn revealed we have to use the right
routing proxy for the promotions controller, otherwise we'd be sent to
actions in the Solidus world.

app/controllers/solidus_friendly_promotions/admin/promotions_controller.rb

@@ -59,6 +59,10 @@ def load_data
       def location_after_save
         solidus_friendly_promotions.edit_admin_promotion_url(@promotion)
       end
+
+      def routes_proxy
+        solidus_friendly_promotions
+      end
     end
   end
 end

config/routes.rb

@@ -2,14 +2,16 @@
 
 SolidusFriendlyPromotions::Engine.routes.draw do
   namespace :admin do
-    resources :promotion_categories, except: [:show]
+    scope :friendly do
+      resources :promotion_categories, except: [:show]
 
-    resources :promotions do
-      resources :promotion_rules
-      resources :promotion_actions
-      resources :promotion_codes, only: [:index, :new, :create]
-      resources :promotion_code_batches, only: [:index, :new, :create] do
-        get "/download", to: "promotion_code_batches#download", defaults: {format: "csv"}
+      resources :promotions do
+        resources :promotion_rules
+        resources :promotion_actions
+        resources :promotion_codes, only: [:index, :new, :create]
+        resources :promotion_code_batches, only: [:index, :new, :create] do
+          get "/download", to: "promotion_code_batches#download", defaults: {format: "csv"}
+        end
       end
     end
   end