[FIX] password_security: update password_write_date on copy

Sometimes users are created from a template user via a `copy()`.
This has the issue that a password is passed via the `vals` of the copy
and therefore never seen by the `write()` function.

As a result, the `password_write_date` field is left to the value of the
template, which is either outdated or null.

A concrete bug that resulted from this is that newly created users were
asked to renew their password on their very first login.

---

This commit reapplies the same logic of the `write()` method to the
`copy()` method as well.

It also changes the unit test test_03_create_user_signup to create the
user at some time in the past so that
```python
assertNotEqual(password_write_date, created_user.password_write_date)
```
makes sense.

password_security/models/res_users.py

@@ -32,6 +32,11 @@ def write(self, vals):
             vals["password_write_date"] = fields.Datetime.now()
         return super(ResUsers, self).write(vals)
 
+    def copy(self, vals):
+        if vals.get("password"):
+            vals["password_write_date"] = fields.Datetime.now()
+        return super(ResUsers, self).copy(vals)
+
     @api.model
     def get_password_policy(self):
         data = super(ResUsers, self).get_password_policy()

password_security/tests/test_signup.py

@@ -4,6 +4,7 @@
 
 from unittest import mock
 
+from freezegun import freeze_time
 from requests.exceptions import HTTPError
 
 from odoo import http
@@ -82,7 +83,8 @@ def test_03_create_user_signup(self):
 
         # Stronger password: no error raised
         vals["password"] = "asdQWE12345_3"
-        login, pwd = self.env["res.users"].signup(vals)
+        with freeze_time("2020-01-01"):
+            login, pwd = self.env["res.users"].signup(vals)
 
         # check created user
         created_user = self.env["res.users"].search([("login", "=", "test_user")])