LP#1468422 auth-internal validate API

LP#1468422 auth-internal validate API

Adds a new open-ils.auth_internal API
open-ils.auth_internal.user.validate for checking whether a user should
be allowed to login.

It tests user existence, active=true, barred=false, deleted=false.

If a barcode is also provided, it confirms the barcode exists and is
active.

Modifies open-ils.auth.authenticate.complete to use the new API instead
of implementing the logic directly.

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Dan Wells <dbw2@calvin.edu>