Bug 13895: Add API routes for checkouts retrieval and renewal

Bug 13895: Add API routes for checkouts retrieval and renewal

GET /checkouts?borrowernumber={borrowernumber}
GET /checkouts/{checkout_id}
PUT /checkouts/{checkout_id}

+ unit tests in t/db_dependent/api/v1/checkouts.t

Test plan:
1. Open a browser tab on Koha staff and log in (to create CGISESSID
   cookie). You should have permission circulate_remaining_permissions.
2. Go to http://yourlibrary/api/v1/checkouts?borrowernumber=XXX (replace
   XXX with a borrowernumber that has checkouts) and check you receive
   correct data
3. Go to http://yourlibrary/api/v1/checkouts/YYY (replace YYY with an
   existing checkout id) and check you receive correct data
4. Send PUT requests to http://yourlibrary/api/v1/checkouts/YYY until
   the maximum number of renewals is reached (you should have a 403
   error)
5. Run unit tests in t/db_dependent/api/v1/checkouts.t

Depends on bugs 16699 and 14868

Signed-off-by: Benjamin Rokseth <benjamin.rokseth@kul.oslo.kommune.no>
Signed-off-by: Lari Taskula <larit@student.uef.fi>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>