<UserStory> 1954: Implement Service Refactoring </UserStory>
UserStory #1954
<Changes>
1. Refactored notification handling to persist notifications directly in the datastore instead of maintaining notification collections within User objects.
2. Removed recipient User pointer dependencies from Notification and retained recipient user identification through recipientUserId.
3. Implemented generic observer persistence support in DataStore with shared helper methods for loading and saving observer subscriptions.
4. Added datastore-backed observer management for ServiceManagementService, PaymentManagementService, and InventoryManagementService.
5. Updated attach() and detach() operations to load, modify, and persist observer subscriptions using shared memory mappings.
6. Refactored sendNotification() implementations to create and persist Notification records directly to the datastore for subscribed observers.
7. Updated UserManagementService notification retrieval and deletion logic to operate on datastore notification records filtered by recipient user ID.
8. Removed notification ownership and observer-specific notification APIs from User and Observer classes.
9. Added configurable shared memory growth factor support and updated mapping expansion logic to use centralized configuration values.
10. Removed obsolete NotificationManagementService implementation and updated project configuration references.
11. Added DataStoreLockGuard integration for observer and notification persistence operations to ensure synchronized datastore access.
</Changes>
<Test>
N/A
</Test>
<Review>
Sreeja Reghukumar, please review
</Review>
joelthomastrenser
Jissin Mathew