[FIX] base_vat: Indonesian 16-digits Tax ID validation

Recently, Indonesia introduced a new tax ID format featuring 16 digits,
replacing the previous 15-digit system. We have implemented support for
this 16-digit tax ID. However, we are currently applying the 15-digit
validation method (Luhn algorithm) to the 16-digit IDs, which doesn't
work.

opw-3727058

closes odoo#153612

Signed-off-by: Brice Bartoletti (bib) <bib@odoo.com>

addons/base_vat/models/res_partner.py

@@ -688,11 +688,12 @@ def check_vat_id(self, vat):
         if len(vat) not in (15, 16) or not vat[0:15].isdecimal() or not vat[-1].isdecimal():
             return False
 
-        # VAT is only digits and of the right length, check the Luhn checksum.
-        try:
-            luhn.validate(vat[0:9])
-        except (InvalidFormat, InvalidChecksum):
-            return False
+        if len(vat) == 15:
+            # VAT is only digits and of the right length, check the Luhn checksum.
+            try:
+                luhn.validate(vat[0:9])
+            except (InvalidFormat, InvalidChecksum):
+                return False
 
         return True