refactor: replace SQL unique constraint with odoo.models.Constraint for hr_employee pin

models/hr_employee.py

@@ -10,13 +10,10 @@ _logger = logging.getLogger(__name__)
 class HrEmployee(models.Model):
     _inherit = 'hr.employee'
 
-    _sql_constraints = [
-        (
-            'pin_unique',
-            'UNIQUE(pin)',
+    _pin_unique = models.Constraint(
+        'unique(pin)',
         'The Employee PIN Code must be unique across all employees and companies.',
     )
-    ]
 
     # ------------------------------------------------------------------
     # Helpers