<UserStory> 1950: Implement Service Refactorings </UserStory>
UserStory #1950
<Changes>
1. Added `DataStoreLockGuard` integration in `PaymentManagementService` methods (`sendPaymentReminders`, `generateInvoice`, `getInvoices`, `completePayment`, `getAllInvoices`, `confirmPayment`) to ensure thread-safe access to the datastore.
2. Implemented record enrichment logic in `DataStore::getInvoices()` to automatically link `Invoice` objects with their corresponding `ServiceBooking` and `InventoryItem` entities during loading, validating relationships and throwing exceptions for invalid references.
3. Refactored invoice persistence by implementing `saveInvoices()` using `saveRecords<Invoice, SerializedInvoice>` to write tracked records directly to shared memory.
4. Updated invoice creation and modification flows:
- `generateInvoice`: Uses `createNewRecord` to insert new invoices into the tracked cache and triggers immediate persistence.
- `completePayment` & `confirmPayment`: Marks records as `MODIFIED` in the `TrackedRecord` state before saving changes.
5. Updated data access patterns across `PaymentManagementService` to use `.data` pointers from `TrackedRecord` objects returned by the datastore, replacing direct pointer access to mapped objects.
6. Added necessary header dependencies including `DataStoreLockGuard.h`, `Invoice.h`, and `SerializedRecords.h` to support locking mechanisms and structured serialization.
</Changes>
<Test>
N/A
</Test>
<Review>
Sreeja Reghukumar, please review
</Review>
Jissin Mathew
7047e96b3c