Implement Service Refactoring

<UserStory> 1958: Service Refactoring </UserStory>
UserStory #1958
<Changes>

1. Added DataStoreLockGuard.h include to project file and InventoryManagementService
   for thread-safe datastore operations.

2. Enhanced DataStore::getUsers to load SerializedUser records, refresh cache,
   and attach notifications with recipient validation.

3. Enhanced DataStore::getInventoryItems to load SerializedInventoryItem records
   and refresh cache for tracked inventory items.

4. Refactored InventoryManagementService::sendLowStockAlerts to use tracked
   inventory and user maps with DataStoreLockGuard, ensuring safe access.

5. Removed legacy observer management, load/save inventory items, and related
   persistence functions from InventoryManagementService.

6. Updated InventoryManagementService::addInventoryItem to insert new records
   into tracked inventory map and persist changes via saveInventoryItems.

7. Updated InventoryManagementService::addInventoryItemStock to validate item
   existence, update quantity, mark record as MODIFIED, and persist changes.

8. Refactored InventoryManagementService::getInventoryItems to return object
   map extracted from tracked records with DataStoreLockGuard.

9. Updated InventoryManagementService::removeInventoryItem to validate item ID,
   mark state as INACTIVE, set record state to MODIFIED, and persist changes.

10. Updated InventoryManagementService::getInventoryItem to safely retrieve
    inventory items from tracked records with error handling.

</Changes>

<Test>

N/A

</Test>

<Review>

Sreeja Reghukumar

</Review>

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/datastores/DataStore.cpp

@@ -228,6 +228,22 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<User>>& DataStore::getUsers()
 {
+    auto users = loadRecords<User, SerializedUser>(m_users);
+    refreshCache(m_userCache, users);
+    auto& notifications = getNotifications();
+    int numberOfNotifications = m_notificationCache.getSize();
+    for (int index = 0; index < numberOfNotifications; index++)
+    {
+        Notification* notification = notifications.getValueAt(index).data;
+        const std::string& recipientUserId = notification->getRecipientUserId();
+        int userIndex = m_userCache.find(recipientUserId);
+        if (userIndex == -1)
+        {
+            throw std::runtime_error("Invalid recipient user ID");
+        }
+        User* user = m_userCache.getValueAt(userIndex).data;
+        user->addNotification(notification);
+    }
     return m_userCache;
 }
 
@@ -280,6 +296,8 @@ Returns:
 */
 util::Map<std::string, TrackedRecord<InventoryItem>>& DataStore::getInventoryItems()
 {
+    auto inventoryItems = loadRecords<InventoryItem, SerializedInventoryItem>(m_inventoryItems);
+    refreshCache(m_inventoryItemCache, inventoryItems);
     return m_inventoryItemCache;
 }
 
@@ -419,6 +437,7 @@ Returns:
 */
 void DataStore::saveInventoryItems()
 {
+    saveRecords<InventoryItem, SerializedInventoryItem>(m_inventoryItems, m_inventoryItemCache);
 }
 
 /*