Update shipping_category usage in admin pages

app/controllers/spree/admin/products_controller.rb

@@ -27,7 +27,7 @@ module Spree
       end
 
       def new
-        @object.shipping_category = DefaultShippingCategory.find_or_create
+        @object.shipping_category_id = DefaultShippingCategory.find_or_create.id
       end
 
       def edit

app/controllers/spree/admin/variants_controller.rb

@@ -19,6 +19,7 @@ module Spree
 
       def edit
         @url_filters = ::ProductFilters.new.extract(request.query_parameters)
+        @object.shipping_category = DefaultShippingCategory.find_or_create
       end
 
       def create
@@ -114,6 +115,7 @@ module Spree
 
       def load_data
         @tax_categories = TaxCategory.order(:name)
+        @shipping_categories = ShippingCategory.order(:name)
       end
     end
   end

app/views/spree/admin/products/_form.html.haml

@@ -38,11 +38,6 @@
 
     .clear
 
-    = f.field_container :shipping_categories do
-      = f.label :shipping_category_id, t(:shipping_categories)
-      = f.collection_select(:shipping_category_id, @shipping_categories, :id, :name, {}, { :class => 'select2' })
-      = f.error_message_on :shipping_category
-
   .clear
 
   %div

app/views/spree/admin/variants/_form.html.haml

@@ -68,4 +68,8 @@
     = f.label :tax_category_id, t(:tax_category)
     = f.collection_select(:tax_category_id, @tax_categories, :id, :name, { include_blank: t(:none) }, { class: 'select2 fullwidth' })
 
+  .field
+    = f.label :shipping_category_id, t(:shipping_categories)
+    = f.collection_select(:shipping_category_id, @shipping_categories, :id, :name, {}, { class: 'select2 fullwidth' })
+
 .clear