Centralize the location for modifying share record tables, e.g. migrate the deleteShare from CloudSharingView to CKSystemSharingUIObserver

[larryonoff]

I’ve started integration of system SWCollaborationView, which allows modifying sharing preferences. For the SWCollaborationView wrapper, SyncMetadata tables need updates (e.g., deleteShare on stop sharing).

I presume that the framework needs a centralized location for monitoring SKShare modifications.

CloudKit offers an option to observe CKSystemSharingUIObserver changes. So CKSystemSharingUIObserver can be used within SyncEngine to modify SyncMetadata tables, e.g. instead of modifying it directly in _CloudSharingDelegate, link

[mbrandonw]

Hi @larryonoff, this seems like a good change to make and we'll look into it soon. Thanks!