Bug 30118: Make holds_block_checkin in SIP behave like in Koha interface.

Bug 30118: Make holds_block_checkin in SIP behave like in Koha interface.

In koha interface, a warning is displayed when an item on hold is returned
only if the return is for this specific item.

This patch does the same in SIP: the return is blocked when holds_block_checkin
is enabled and there is a hold on a specific item and this is the very item
being returned.

Test plan:

The following behavior is expected in SIP:

 - An item is returned, and there is a reservation on record-level: block
 - An item is returned, and there is a reservation on this very item: block
 - An item is returned, and there is a reservation on another item: allow

Signed-off-by: Sonia <sonia.bouis@univ-lyon3.fr>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>