Bug 31086: (QA follow-up) Add unit tests

Bug 31086: (QA follow-up) Add unit tests

This patch adds the unit tests for the change to Koha::Hold::store.

We test for and catch the exception introduced for both the create and
update cases.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
(cherry picked from commit f0685f0f4053da428ab13d9f3991790fb71b7e55)

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
(cherry picked from commit bc95ffa3e3f97738f54ce56e2af0422bfc05bc57)
Signed-off-by: Arthur Suzuki <arthur.suzuki@biblibre.com>