Bug 24003: Make the API set userenv on authentication

Bug 24003: Make the API set userenv on authentication

This patch makes the authentication step stash the user that got
authenticated so code outside the Mojo part of Koha can use it (i.e.
through the use of C4::Context->userenv).

To test:
1. Apply the regression tests
2. Run:
   $ kshell
  k$ prove t/db_dependent/api/v1/auth_authenticate_api_request.t \
           t/db_dependent/api/v1/auth_basic.t
=> FAIL: Tests fail!
3. Apply this patch
4. Repeat 2
=> SUCCESS: Tests pass!

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>