Comment 8 for bug 2012971

Here is a branch for this:
collab/phasefx/lp2012971-item-alerts-not-editable

From the commit message:
Release-notes: Fixes invocation of (Manage) Item Alerts dialog in Holdings Editor
Release-notes: Adds batch edit for Item Alerts in Holdings Editor. Alerts get grouped together for editing if they are mostly identical
Release-notes: Adds Manage Alerts button to Item Alerts dialog during alert display in Angular ("eg2") interfaces.
Release-notes: Fixes TypeError: defaults is null exception for missing Default Item Alert Type preference
Release-notes: Adds a Changes Pending indicator for Holdings Editor

Note that we do not address LP2044028 where multiple invocations of the
Item Alerts dialog in the Holdings Editor do not show pending changes
prior to a Save.

Example testing:

In staff client with Concerto dataset,
Cataloging -> Retrieve Bib Record By ID -> 1
Holdings View -> Show Copies
Select lines 5 and 6 (for CONC40000536 and CONC41000536)
-> Edit: Edit Items
-> Add Item Alerts: Item Alerts
Should see a dialog for "Managing alerts in common for 2 item(s)."
Normal Checkout, Test Note 123 -> Add New, Apply Changes
Should see a CHanges Pending label before Apply All & Save
Apply All, Save & Exit

Back in Holdings View,
Select lines 5 and 8 (for CONC40000536 and CONC4000036)
-> Edit: Edit Items
-> Add Item Alerts: Item Alerts
Should see a dialog for "Managing alerts in common for 2 item(s)."
Should not see the "Test Note 123" alert.
Close tab

Back in Holdings View,
Select lines 5 and 6 again
-> Edit: Edit Items
-> Add Item Alerts: Item Alerts
Should see a dialog for "Managing alerts in common for 2 item(s)."
Should also see the "Test Note 123" alert.
Close tab

Circulation -> Check Out
99999372363 -> Submit
In the URL, change /eg/ to /eg2/ for the experimental Angular circ interface
CONC40000536 -> Submit
Should see the Item Alerts dialog with the Test Note 123 alert.
Should also see a Manage Alerts button in the dialog.
Manage Alerts
Should see a new dialog, "Managing alerts for item CONC40000536",
which is the same Item Alerts dialog from the Holdings Editor.
Changes in this dialog are not reflected in the original Item Alerts
dialog from which it was spawned.