Bug 32739: Allow other patron identifier on pwd validation

Bug 32739: Allow other patron identifier on pwd validation

This patch takes a step forward on the password validation endpoint, by
adding  the `identifier` parameter and making it be allowed
to be the patron's `cardnumber` or the `userid`.

The current `userid` only validation option is kept as-is.

The implementation relies on `C4::Auth::checkpw` to query for the
patron.

To test:
1. Apply this patches
2. Run:
   $ ktd --shell
  k$ prove t/db_dependent/api/v1/password_validation.t
=> SUCCESS: Tests pass!
3. Sign off :-D

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>