Bug 36084: Add CSRF token support to svc/authentication

Bug 36084: Add CSRF token support to svc/authentication

GET svc/authentication will return a CSRF token in a response header

POST svc/authentication requires a CSRF token which can be sourced
from the response header of GET svc/authentication or some other
place like the meta element on a HTML page

Note: misc/migration_tools/koha-svc.pl is a simple script which
can be used to practically evaluate svc/authentication and svc/bib

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>