Add default lead time on product configuration

Changeset 0a0b8be85ef5 added a default value for the multivalue model, but
not for the product configuration, so it is always ignored.

Closes #14188

modules/sale/product.py

@@ -27,13 +27,18 @@ class Configuration(metaclass=PoolMeta):
 
     default_lead_time = fields.MultiValue(default_lead_time)
 
+    @classmethod
+    def default_default_lead_time(cls, **pattern):
+        return cls.multivalue_model(
+            'default_lead_time').default_default_lead_time()
+
 
 class DefaultLeadTime(ModelSQL, ValueMixin):
     __name__ = 'product.configuration.default_lead_time'
     default_lead_time = default_lead_time
 
     @classmethod
-    def default_default_lead_time(cls, **pattern):
+    def default_default_lead_time(cls):
         return datetime.timedelta(0)