pass first 2 bill tests

Signed-off-by: Nico Schottelius <nico@nico-notebook.schottelius.org>

uncloud_pay/models.py

@@ -399,8 +399,8 @@ class Bill(models.Model):
 
     @property
     def sum(self):
-        return 0
-#        for self.billrecord_set.
+        bill_records = BillRecord.objects.filter(bill=self)
+        return sum([ br.sum for br in bill_records ])
 
 
     @classmethod
@@ -525,9 +525,10 @@ class BillRecord(models.Model):
     starting_date = models.DateTimeField()
     ending_date = models.DateTimeField()
 
+    @property
     def quantity(self):
         """ Determine the quantity by the duration"""
-        if self.order.is_recurring:
+        if self.order.is_one_time:
             return 1
 
         record_delta = self.ending_date - self.starting_date
@@ -535,6 +536,7 @@ class BillRecord(models.Model):
         return record_delta.total_seconds()/self.order.recurring_period
 
 
+    @property
     def sum(self):
         return self.order.price * self.quantity