Implement View Stock Level Functionality

<UserStory> INV001: View Stock Level </UserStory>

<Changes>
    1. Integrated InventoryManagementService into Controller to provide read-only access to inventory items.
    2. Added implementation for InventoryManagementService::getInventoryItems to fetch data from DataStore.
    3. Enhanced AdminMenu with viewStockLevels functionality to display inventory details (ID, part name, quantity, price).
    4. Updated NotificationManagementService interface to provide concrete implementations for sendNotification, attach, detach, and notify methods.
    5. Included necessary headers (InventoryItem, InventoryManagementService, iomanip) for new functionality.
</Changes>

<Test>

  Precondition:
  1. Admin user is logged into the system.
  2. Inventory contains multiple items with varying stock levels.
  3. Notification service is active and users are registered.

  Steps:
  1. Navigate to Admin Menu and select "View Stock Levels".
    - Verify that the system displays all inventory items with ID, part name, quantity, and price.
  2. Check items with sufficient stock.
    - Verify that they are displayed normally without highlighting.
  3. Check items with low stock threshold.
    - Verify that these items are highlighted to indicate low availability.
  4. Trigger a notification for a low-stock item.
    - Verify that the notification is sent to registered users successfully.
</Test>

<Review>
Sreeja Reghukumar
</Review>

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/controllers/Controller.cpp

@@ -50,7 +50,14 @@ void Controller::purchaseComboPackage(const std::string& comboPackageID, const s
 
 util::Map<std::string, const InventoryItem*> Controller::getInventoryItems()
 {
-    return util::Map<std::string, const InventoryItem*>();
+    auto inventoryIems = m_inventoryManagementService.getInventoryItems();
+    util::Map<std::string, const InventoryItem*> readOnlyInventoryItems;
+    int inventoryItemsMapSize = inventoryIems.getSize();
+    for (int index = 0; index < inventoryItemsMapSize; index++)
+    {
+        readOnlyInventoryItems.insert(inventoryIems.getKeyAt(index), inventoryIems.getValueAt(index));
+    }
+    return readOnlyInventoryItems;
 }
 
 const InventoryItem* Controller::getInventoryItem(const std::string& inventoryItemID)

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/controllers/Controller.h

@@ -2,6 +2,7 @@
 #include "Map.h"
 #include <string>
 #include "Enums.h"
+#include "InventoryManagementService.h";
 
 class Service;
 class ComboPackage;
@@ -14,6 +15,8 @@ class Notification;
 
 class Controller
 {
+private:
+    InventoryManagementService m_inventoryManagementService;
 public:
     bool login(const std::string& username, const std::string& password);
     void logout();

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/InventoryManagementService.cpp

@@ -1 +1,6 @@
 #include "InventoryManagementService.h"
+
+util::Map<std::string, InventoryItem*> InventoryManagementService::getInventoryItems()
+{
+	return m_dataStore.getInventoryItems();
+}

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/AdminMenu.cpp

@@ -1,4 +1,6 @@
+#include <iomanip>
 #include "AdminMenu.h"
+#include "InventoryItem.h"
 #include "InputHelper.h"
 #include "OutputHelper.h"
 
@@ -42,6 +44,27 @@ void AdminMenu::changePassword()
 
 void AdminMenu::viewStockLevels()
 {
+	auto inventoryItems = m_controller.getInventoryItems();
+	std::cout << std::left << std::setw(15) << "Item ID"
+		<< std::setw(25) << "Part Name"
+		<< std::setw(10) << "Quantity"
+		<< std::setw(10) << "Price"
+		<< std::endl;
+	for (int iterator = 0; iterator < inventoryItems.getSize(); ++iterator)
+	{
+		const InventoryItem* item = inventoryItems.getValueAt(iterator);
+		if (item != nullptr)
+		{
+			if (item->getState() != util::State::INACTIVE)
+			{
+				std::cout << std::left << std::setw(15) << item->getId()
+					<< std::setw(25) << item->getPartName()
+					<< std::setw(10) << item->getQuantity()
+					<< std::setw(10) << item->getPrice()
+					<< std::endl;
+			}
+		}
+	}
 }
 
 void AdminMenu::addInventoryItem()