Bug 26274: Add cashups api routes

Bug 26274: Add cashups api routes

This patch creates a Koha::Cash::Register::Cashup(s) class pair which
subclass Koha::Cash::Register::Action(s) and moves the cashup specific
code into these new classes to improve code separation.

We then introduce API routes based on these classes to allow fetching
a list of cashups associated to a cash register and a full cashup with
emeddable summary for individual cashups.

Test plan
1/ Run the updated unit tests.
   t/db_dependent/Koha/Cash/Register/Action.t
   t/db_dependent/Koha/Cash/Register/Cashup.t
2/ Run the incuded api tests.
   t/db_dependent/api/v1/cashups.t

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>