[IMP] account: add generic base_vat methods to enable vat validation without the dependency

To enable VAT validation (VIES/ simple), the base_vat module needs to be installed.
base_vat extends models where the validation should apply. This means it only works with models in account, unless the module is added as a dependency (base_vat depends on account)
To avoid this dependency (in account reports - see enterprise PR odoo/enterprise#34068), two methods required for VAT validation are added to res.partner so that the enterprise module is able to use this feature with/without base_vat.

closes odoo/odoo#106046

Signed-off-by: Olivier Colson (oco) <oco@odoo.com>

addons/account/models/partner.py

@@ -667,6 +667,35 @@ class ResPartner(models.Model):
                     raise e
                 _logger.debug('Another transaction already locked partner rows. Cannot update partner ranks.')
 
+    @api.model
+    def _run_vat_test(self, vat_number, default_country, partner_is_company=True):
+        """ Checks a VAT number syntactically to ensure its validity upon saving.
+
+        :param vat_number: a string with the VAT number to check.
+        :param default_country: a res.country object
+        :param partner_is_company: True if the partner is a company, else False.
+            .. deprecated:: 16.0
+                Will be removed in 16.2
+
+        :return: The country code (in lower case) of the country the VAT number
+                 was validated for, if it was validated. False if it could not be validated
+                 against the provided or guessed country. None if no country was available
+                 for the check, and no conclusion could be made with certainty.
+        """
+        return default_country.code.lower()
+
+    @api.model
+    def _build_vat_error_message(self, country_code, wrong_vat, record_label):
+        """ Prepare an error message for the VAT number that failed validation
+
+        :param country_code: string of lowercase country code
+        :param wrong_vat: the vat number that was validated
+        :param record_label: a string to desribe the record that failed a VAT validation check
+
+        :return: The error message string
+        """
+        return ""
+
     @api.model
     def get_partner_localisation_fields_required_to_invoice(self, country_id):
         """ Returns the list of fields that needs to be filled when creating an invoice for the selected country.

addons/base_vat/models/res_partner.py

@@ -192,21 +192,7 @@ class ResPartner(models.Model):
 
     @api.model
     def _run_vat_test(self, vat_number, default_country, partner_is_company=True):
-        """ Checks a VAT number syntactically to ensure its validity upon saving.
-        A first check is made by using the first two characters of the VAT as
-        the country code. If it fails, a second one is made using default_country instead.
-
-        :param vat_number: a string with the VAT number to check.
-        :param default_country: a res.country object
-        :param partner_is_company: True if the partner is a company, else False.
-            .. deprecated:: 16.0
-                Will be removed in 16.2
-
-        :return: The country code (in lower case) of the country the VAT number
-                 was validated for, if it was validated. False if it could not be validated
-                 against the provided or guessed country. None if no country was available
-                 for the check, and no conclusion could be made with certainty.
-        """
+        # OVERRIDE account
         check_result = None
 
         # First check with country code as prefix of the TIN
@@ -256,6 +242,7 @@ class ResPartner(models.Model):
 
     @api.model
     def _build_vat_error_message(self, country_code, wrong_vat, record_label):
+        # OVERRIDE account
         if self.env.context.get('company_id'):
             company = self.env['res.company'].browse(self.env.context['company_id'])
         else: