doc(auth): Warn about disabled token passwords and LDAP logout

doc(auth): Warn about disabled token passwords and LDAP logout

Auth tokens store the user's login password by default. If the password
changes externally (on LDAP), all connected clients stop syncing after 5
minutes max when the password is verified the next time. A web login
revivess those app passwords.

If storing the password is disabled, the tokens continue to work after
password change. But that also means the clients are not logged out the
same way. This can be fine for some setups and problematic for others.

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>