Test that creating products w/o correct billing address fails

uncloud_pay/models.py

@@ -789,8 +789,25 @@ class Product(UncloudModel):
             # FIXME: use the right type of exception here!
             raise Exception("Did not implement the discounter for this case")
 
+
+    def save(self, *args, **kwargs):
+        try:
+            ba = BillingAddress.get_address_for(self.owner)
+        except BillingAddress.DoesNotExist:
+            raise ValidationError("User does not have a billing address")
+
+        if not ba.active:
+            raise ValidationError("User does not have an active billing address")
+
+        super().save(*args, **kwargs)
+
+
 # Sample products included into uncloud
 class SampleOneTimeProduct(Product):
+    """
+    Products are usually more complex, but this product shows how easy
+    it can be to create your own one time product.
+    """
 
     default_recurring_period = RecurringPeriod.ONE_TIME
 
@@ -801,6 +818,11 @@ class SampleOneTimeProduct(Product):
         return self.ot_price
 
 class SampleRecurringProduct(Product):
+    """
+    Products are usually more complex, but this product shows how easy
+    it can be to create your own recurring fee product.
+    """
+
     default_recurring_period = RecurringPeriod.PER_30D
 
     rc_price = models.IntegerField(default=10)
@@ -810,6 +832,11 @@ class SampleRecurringProduct(Product):
         return self.rc_price
 
 class SampleRecurringProductOneTimeFee(Product):
+    """
+    Products are usually more complex, but this product shows how easy
+    it can be to create your own one time + recurring fee product.
+    """
+
     default_recurring_period = RecurringPeriod.PER_30D
 
     ot_price = models.IntegerField(default=5)