Bug 28130: Manage a patron's subscription alerts

Bug 28130: Manage a patron's subscription alerts

This enhancement adds an 'Alert subscriptions' page to a patron account to easily view or cancel email alerts the patron has subscribed to.

To test:

1. Go to Cataloging. Create a biblio.
2. Go to Tools -> Notices & slips. Create a notice under the "Serials (new issue)" module, if you don't already have one.
3. Go to Serials. Create a subscription. Link the biblio you just created. Add info like the callnumber, location, library. Choose your notice under Patron notification. Fill out the remaining details and save your subscription.
4. Open this record in the OPAC. Under the Subscriptions tab, click the button to "Subscribe to email notification on new issues"
5. Go back to the staff interface. Go to your patron account.
6. Notice there is a new "Alert subscriptions" tab in the left sidebar menu. The number in brackets should say 1, for the subscription you just enabled email alerts.
7. Click into the page. Confirm your subscription shows in the table.
8. Click the button to unsubscribe. A confirmation should pop up. Confirm you can cancel the unsubscribe action. Then confirm you can unsubscribe using this button.
9. Confirm tests pass t/db_dependent/Koha/Patron.t

Sponsored-by: Bibliotheksservice-Zentrum Baden-Wuerttemberg
Signed-off-by: Christian Stelzenmüller <christian.stelzenmueller@bsz-bw.de>
Signed-off-by: Sam Lau <samalau@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>