[FIX] account: less restriction on tax.name

The aim of this commit is to allow having several taxes with the same
name if those taxes are from different countries.

Context:
With the new taxonomy, it was much more likely for 2 taxes to have the
same name and that was the case for several taxes.

Before this commit:
It was impossible to instantiate some foreign tax because of the unicity
on tax name constrains.

After this commit:
- Foreign tax with same name than national tax can be created again
- UX is improved by appending the country code to the tax name for
  display purpose.

closes odoo/odoo#137921

Task-id: None
X-original-commit: 502ec287590b95fdae581cc048ca25eb6699e16d
Signed-off-by: William André (wan) <wan@odoo.com>
Signed-off-by: Brice Bartoletti (bib) <bib@odoo.com>

addons/account/models/account_tax.py

@@ -186,6 +186,7 @@ class AccountTax(models.Model):
                     ('name', '=', record.name),
                     ('type_tax_use', '=', record.type_tax_use),
                     ('tax_scope', '=', record.tax_scope),
+                    ('country_id', '=', record.country_id.id),
                     ('id', '!=', record.id),
                 ])
         if duplicates := self.search(expression.OR(domains)):
@@ -383,6 +384,8 @@ class AccountTax(models.Model):
                 name += ' (%s)' % tax_scope.get(record.tax_scope)
             if len(self.env.companies) > 1 and self.env.context.get('params', {}).get('model') == 'product.template':
                 name += ' (%s)' % record.company_id.display_name
+            if record.country_id != record.company_id.account_fiscal_country_id:
+                name += ' (%s)' % record.country_code
             record.display_name = name
 
     @api.onchange('amount')

addons/account/tests/test_multivat.py

@@ -100,8 +100,8 @@ def data_method_provider(chart_template_name, country_code):
             'account.tax': {
                 xmlid: _tax_vals(name, amount, external_id_prefix)
                 for name, xmlid, amount in (
-                    (f'{external_id_prefix}Tax 1', 'test_tax_1_template', 15),
-                    (f'{external_id_prefix}Tax 2', 'test_tax_2_template', 0),
+                    ('Tax 1', 'test_tax_1_template', 15),
+                    ('Tax 2', 'test_tax_2_template', 0),
                 )
             },
         }