Bug 17617: Confirmation email to patron when hold is placed

Bug 17617: Confirmation email to patron when hold is placed

This enhancement adds a new notice HOLDPLACED_PATRON that will be sent to a patron when a hold is placed for them. It depends on the new system preference EmailPatronWhenHoldIsPlaced to be enabled.

To test:
1) Update database and restart services
2) Go to Koha Administration -> System preferences and search for the new EmailPatronWhenHoldIsPlaced syspref. It should be disabled by default - leave it disabled for now.
3) Search for a record and go to the Holds tab. Place a hold for your patron.
4) Go to your patron's account and go to the Notices tab. Confirm the HOLDPLACED_PATRON notice was NOT queued.
5) Enable the EmailPatronWhenHoldIsPlaced syspref.
6) Repeat steps 3 and 4. Confirm the HOLDPLACED_PATRON notice WAS generated and queued.
7) Confirm tests pass t/db_dependent/Holds.t

Sponsored-by: Fire and Emergency New Zealand
Signed-off-by: Kelly <kelly@bywatersolutions.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>