Bug 36120: Add pickup_items to the pickup_locations response

Bug 36120: Add pickup_items to the pickup_locations response

This patch adds pickup_items as a list of itemnumbers that can be picked
from the library should it be selected as a pickup location.

Sponsored-by: Cuyahoga County Public Library
Signed-off-by: Lisette Scheer <lisette.scheer@bywatersolutions.com>
Signed-off-by: Kristi Krueger <kkrueger@cuyahogalibrary.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>