No pickup notice sent to requester if item becomes available because previous request is cancelled/expires while the item is on the holdshelf

Originally reported in: Chalmers Honeysuckle environment, reproduced in Snapshot 2021-04-29.
Reporting library priority: Important. This is a bug that affects patrons directly.

Overview: Pickup notices are not sent when the requested item becomes available through cancellation or expiration while it is already on the holdshelf for another requester. It seems like the event that triggers the notice to be sent does not take place in the scenario where the request becomes available for a new requester while already on the hold shelf.

Preconditions:
Notice policy that sends a notice to the requester when a requested item is available for them to pickup.

Steps to Reproduce:

1. Create a request on item A for user test1
2. Create a request on item A for user test2
3. Check in item A at the pickup service point
4. In Circ log, verify that test1's request now has status Open - Awaiting pickup. It does.
5. In Circ log, verify that a pickup notice has been sent to test1. It has.
   
6. Cancel the request, or let the the hold shelf expiration date/time pass
7. Due to cancellation/expiration, the request becomes available to the next person in the queue
8. In Circ log, verify that user test2's request now has status Open - Awaiting pickup. It does.
9. In Circ log, verify that a pickup notice has been sent to test2.

Expected Results:
There is a circ log entry showing that a pickup notice has been sent to test2. The user has received an email.

Actual Results:
There is no circ log entry showing that a pickup notice has been sent to user2. The user has received no email.

Additional Information:
It looks like the event triggering the notice does not take place when a request is cancelled/expires while on the holdshelf for another requester.
I tried some more action to see what would actually trigger it:

Checking the item in at the pickup service point did not trigger a notice.
Checking the item in at another service point, thereby changing its status to In transit, and then checking it in at the pickup service point did the trick. A notice was sent.

See the full series of event in this screenshot:

URL: https://folio-snapshot.dev.folio.org/

Interested parties: MarieWi