pre-fix ZIP with state code (if state assigned + code exists)

There are some countries (notably US + Canada) where the ZIP is
customarily prefixed with the two-letter state code.

Fixes: SYS#3625

models/dp_delivery_carrier.py

@@ -54,10 +54,15 @@ class DPDeliveryCarrier(models.Model):
         street2 = None
         if partner.street2:
             street2 = partner.street2
+        # Countries like the US have state codes preceeding the ZIP
+        if partner.state_id and partner.state_id.code:
+            zipcode = "%s %s" % (partner.state_id.code, partner.zip)
+        else:
+            zipcode = partner.zip
         addr = im.build_addr(street = street,
                              house = house,
                              additional = street2,
-                             zipcode = partner.zip,
+                             zipcode = zipcode,
                              city = partner.city,
                              country = country)
         if partner.is_company: