IMP point_of_sale: make overrideable default field method

In case of import of data in pos.config you may want
your data being inserted with another user
than superadmin. This fix allows to manage
the behavior by make it possible to override these methods

addons/point_of_sale/models/pos_config.py

@@ -40,18 +40,34 @@ class PosConfig(models.Model):
     _description = 'Point of Sale Configuration'
 
     def _default_sale_journal(self):
+        return default_sale_journal()
+
+    def default_sale_journal(self):
+        # overidable method
         journal = self.env.ref('point_of_sale.pos_sale_journal', raise_if_not_found=False)
         if journal and journal.sudo().company_id == self.env.user.company_id:
             return journal
         return self._default_invoice_journal()
 
     def _default_invoice_journal(self):
+        return default_invoice_journal()
+
+    def default_invoice_journal(self):
+        # overidable method
         return self.env['account.journal'].search([('type', '=', 'sale'), ('company_id', '=', self.env.user.company_id.id)], limit=1)
 
     def _default_pricelist(self):
+        return default_pricelist()
+
+    def default_pricelist(self):
+        # overidable method
         return self.env['product.pricelist'].search([('currency_id', '=', self.env.user.company_id.currency_id.id)], limit=1)
 
     def _get_default_location(self):
+        return get_default_location()
+
+    def get_default_location(self):
+        # overidable method
         return self.env['stock.warehouse'].search([('company_id', '=', self.env.user.company_id.id)], limit=1).lot_stock_id
 
     def _get_group_pos_manager(self):