Fix invoice and api serializer

app/serializers/api/product_serializer.rb

@@ -10,7 +10,6 @@ class Api::ProductSerializer < ActiveModel::Serializer
   has_many :variants, serializer: Api::VariantSerializer
 
   has_one :image, serializer: Api::ImageSerializer
-  has_one :supplier, serializer: Api::IdSerializer
 
   # return an unformatted descripton
   def description

app/serializers/api/variant_serializer.rb

@@ -9,6 +9,8 @@ class Api::VariantSerializer < ActiveModel::Serializer
              :tag_list, :thumb_url,
              :unit_price_price, :unit_price_unit
 
+  has_one :supplier, serializer: Api::IdSerializer
+
   delegate :price, to: :object
 
   def fees

app/serializers/invoice/product_serializer.rb

@@ -3,6 +3,5 @@
 class Invoice
   class ProductSerializer < ActiveModel::Serializer
     attributes :name
-    has_one :supplier, serializer: Invoice::EnterpriseSerializer
   end
 end

app/serializers/invoice/variant_serializer.rb

@@ -4,5 +4,6 @@ class Invoice
   class VariantSerializer < ActiveModel::Serializer
     attributes :id, :display_name, :options_text
     has_one :product, serializer: Invoice::ProductSerializer
+    has_one :supplier, serializer: Invoice::EnterpriseSerializer
   end
 end