[FIX] hr: Allow to access employee profile

The `private_email`, `last_check_in` and `last_check_in`
fields were added by e9d98982 to the
profile view but not in `SELF_READABLE_FIELDS`.
A simple user was therefore not able to read the field and
access his profile.

To avoid any similar oversight in the future, a test is added
to ensure a simple user is able to read all fields in
the profile view.