[FIX] hr_holidays: Remove related on employee's department

- In SaaS-16 we have added a related on the employee's department.
    This causes access rights issues when changing the employee's department.
    We do not want to rewrite all the old records, only the new ones should use the new employee's department.

addons/hr_holidays/models/hr.py

@@ -218,7 +218,12 @@ class Employee(models.Model):
 
     def write(self, values):
         res = super(Employee, self).write(values)
-        if 'parent_id' in values:
+        if 'parent_id' in values or 'department_id' in values:
             holidays = self.env['hr.holidays'].search([('state', 'in', ['draft', 'confirm']), ('employee_id', 'in', self.ids)])
-            holidays.write({'manager_id': values['parent_id']})
+            hr_vals = {}
+            if values.get('parent_id') is not None:
+                hr_vals['manager_id'] = values['parent_id']
+            if values.get('department_id') is not None:
+                hr_vals['department_id'] = values['department_id']
+            holidays.write(hr_vals)
         return res

addons/hr_holidays/models/hr_holidays.py

@@ -197,7 +197,7 @@ class Holidays(models.Model):
              "\nChoose 'Allocation Request' if you want to increase the number of leaves available for someone")
     parent_id = fields.Many2one('hr.holidays', string='Parent')
     linked_request_ids = fields.One2many('hr.holidays', 'parent_id', string='Linked Requests')
-    department_id = fields.Many2one('hr.department', related='employee_id.department_id', string='Department', readonly=True, store=True)
+    department_id = fields.Many2one('hr.department', string='Department', readonly=True)
     category_id = fields.Many2one('hr.employee.category', string='Employee Tag', readonly=True,
         states={'draft': [('readonly', False)], 'confirm': [('readonly', False)]}, help='Category of Employee')
     holiday_type = fields.Selection([
@@ -216,6 +216,7 @@ class Holidays(models.Model):
     @api.onchange('employee_id')
     def _onchange_employee_id(self):
         self.manager_id = self.employee_id and self.employee_id.parent_id
+        self.department_id = self.employee_id and self.employee_id.department_id
 
     @api.multi
     @api.depends('number_of_days_temp', 'type')