+ yuan_rate_last_updated in GlobalSettings serializer

* Show raw yuan_rate in GlobalSettings
* Use yuan_rate+yuan_rate_commission sum for Checklist calculations

store/models.py

@@ -81,10 +81,9 @@ class GlobalSettings(models.Model):
                 self.yuan_rate = rate
                 self.yuan_rate_last_updated = timezone.now()
                 self.save()
-                return rate
 
         # Default
-        return self.yuan_rate
+        return self.yuan_rate + self.yuan_rate_commission
 
 
 class Category(MPTTModel):

store/serializers.py

@@ -211,14 +211,15 @@ class AnonymousUserChecklistSerializer(ChecklistSerializer):
 
 
 class GlobalSettingsSerializer(serializers.ModelSerializer):
-    currency = serializers.DecimalField(source='get_yuan_rate', read_only=True, max_digits=10, decimal_places=2)
+    currency = serializers.DecimalField(source='yuan_rate', read_only=True, max_digits=10, decimal_places=2)
+    yuan_rate_last_updated = serializers.DateTimeField(read_only=True)
     chinadelivery = serializers.DecimalField(source='delivery_price_CN', max_digits=10, decimal_places=2)
     commission = serializers.DecimalField(source='commission_rub', max_digits=10, decimal_places=2)
     pickup = serializers.CharField(source='pickup_address')
 
     class Meta:
         model = GlobalSettings
-        fields = ('currency', 'yuan_rate_commission', 'commission',  'chinadelivery', 'pickup', 'time_to_buy')
+        fields = ('currency', 'yuan_rate_last_updated', 'yuan_rate_commission', 'commission',  'chinadelivery', 'pickup', 'time_to_buy')
 
 
 class PaymentMethodSerializer(serializers.ModelSerializer):