Feat(SolidusPromotions): Allow viewing both promotion systems

Prior to this commit, the new promotion system would exchange the
promotion and promotion category index page components if the gem was
loaded. This made it impossible to actually see the old promotion
configuration when using the new admin.

This commit now only changes the orders/index component if the new
promotion system is activated. In any case, it will display new
promotion and promotion category records under "Promotions (new)".

promotions/lib/controllers/admin/solidus_promotions/promotion_categories_controller.rb

@@ -13,7 +13,7 @@ def index
       set_page_and_extract_portion_from(promotion_categories)
 
       respond_to do |format|
-        format.html { render component("promotion_categories/index").new(page: @page) }
+        format.html { render component("solidus_promotions/categories/index").new(page: @page) }
       end
     end
 

promotions/lib/controllers/admin/solidus_promotions/promotions_controller.rb

@@ -19,7 +19,7 @@ def index
       set_page_and_extract_portion_from(promotions)
 
       respond_to do |format|
-        format.html { render component("promotions/index").new(page: @page) }
+        format.html { render component("solidus_promotions/promotions/index").new(page: @page) }
       end
     end
 

promotions/lib/solidus_promotions/engine.rb

@@ -52,11 +52,14 @@ class Engine < Rails::Engine
       end
     end
 
-    initializer "solidus_promotions.add_admin_order_index_component", after: "solidus_legacy_promotions.add_admin_order_index_component" do
+    initializer "solidus_promotions.add_admin_order_index_component", after: "spree.load_config_initializers" do
       if SolidusSupport.admin_available?
-        SolidusAdmin::Config.components["orders/index"] = "SolidusPromotions::Orders::Index::Component"
-        SolidusAdmin::Config.components["promotions/index"] = "SolidusPromotions::Promotions::Index::Component"
-        SolidusAdmin::Config.components["promotion_categories/index"] = "SolidusPromotions::PromotionCategories::Index::Component"
+        if Spree::Config.promotions.is_a?(SolidusPromotions::Configuration)
+          SolidusAdmin::Config.components["orders/index"] = "SolidusPromotions::Orders::Index::Component"
+        end
+
+        SolidusAdmin::Config.components["solidus_promotions/promotions/index"] = "SolidusPromotions::Promotions::Index::Component"
+        SolidusAdmin::Config.components["solidus_promotions/categories/index"] = "SolidusPromotions::PromotionCategories::Index::Component"
       end
     end