Bug 22456: Staff interface handling

Bug 22456: Staff interface handling

This patch introduces a new tab to the 'Holds awaiting pickup' screen
for holds that have cancellation requests. This can be accepted (by
cancelling the hold) or rejected.

To test:
1. Set circulation rules for cancellation requests, allowing them for
   certain item type.
2. Have some waiting holds for a patron on an item type that allows
   requesting cancellation.
3. Visit 'Holds awaiting pickup'
=> SUCCESS: No holds have cancellation requests
4. In the OPAC, on the user details, notice some holds have the ability
   to be requested cancellation.
5. Choose to request cancellation
=> SUCCESS: Request is placed, the button is disabled
6. In 'Holds awaiting pickup' you can see them
7. Play with rejecting/accepting
=> SUCCESS: It works!
8. Things are reflected in the OPAC side

Sponsored-by: Montgomery County Public Libraries
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>