fix(settings): new passwords pass Django's password validators

AUTH_PASSWORD_VALIDATORS was unset, so the user forms and the password
change accepted any password, a one-letter one included. The template
now sets Django's four standard validators: at least 8 characters, not
a common password, not only digits, not like the user's name or e-mail.
The tests that set weak passwords use ones the validators accept.

admin/tests/test_views.py

@@ -105,7 +105,7 @@ class AdminTestCase(TestCase):
             reverse("admin:user_create"),
             {
                 "username": "test",
-                "password": "test",
+                "password": "Wvc-created-9",
                 "role": "user",
                 "max_instances": 1,
                 "max_cpus": 1,