[FIX] hr_contract: Allow HR user to read first contract date

An HR user (without any rights on contracts) could not open
an employee form view since it needs the `first_contract_date`
field which needs contracts access rights.

closes odoo/odoo#47561

X-original-commit: 14855eee0f9c5737ee5aaa792defe88e138e0d7d
Signed-off-by: lul-odoo <LucasLefevre@users.noreply.github.com>

addons/hr_contract/models/hr_employee.py

@@ -21,7 +21,7 @@ class Employee(models.Model):
     @api.depends('contract_ids.state')
     def _compute_first_contract_date(self):
         for employee in self:
-            contracts = employee.contract_ids.filtered(lambda c: c.state != 'cancel')
+            contracts = employee.sudo().contract_ids.filtered(lambda c: c.state != 'cancel')
             if contracts:
                 employee.first_contract_date = min(contracts.mapped('date_start'))
             else: