Bug 23116: AllowHoldPolicyOverride allows a librarian to almost place a hold on an...

Bug 23116: AllowHoldPolicyOverride allows a librarian to almost place a hold on an item already on hold

A library appears to be able to place a second item level hold on an item a patron already has on hold if
A) AllowHoldPolicyOverride is enabled
and
B) the circ rule allow for multple item level holds.

Once the patron submits the hold requests though, the hold does not get stored in the database.

Because allowing two item level holds for the same item makes no sense, we should not allow
this attempt to take place, even if AllowHoldPolicyOverride is enabled.

Test Plan:
 1) Enable AllowHoldPolicyOverride
 2) Set up circ rules to allow for multiple item level holds on one record
 3) Place an item level hold on a record
 4) Note you can force placing a second item hold on that reocrd
 5) Attempt to do so, it will not actually work
 6) Apply this patch
 7) Note you can no longer place another item level hold for the same item
   you just placed an item-level hold on
 8) Note you can still force holds that contravene the circ rules for
   any and all other reasons
 9) Test with record level holds
10) Test by placing multiple holds from search results

Signed-off-by: Martha Fuerst <mfurest@hmcpl.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Simple fix for a regression. Works as expected.
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>