Commit aee6356e: Implement Confirm Payment Functionality

<User Story> Complete Payments - 1797</User Story>

<Changes>
1. Added Controller::getAllInvoices
   - Retrieves all invoices from PaymentManagementService and returns them as a read-only map.
2. Implemented Controller::confirmPayment
   - Delegates payment confirmation for a given invoice ID to PaymentManagementService.
3. Introduced PaymentManagementService::getAllInvoice
   - Provides access to all invoices stored in the datastore.
4. Added PaymentManagementService::confirmPayment
   - Confirms payment for a specific invoice, updates payment date and status, and sends notification.
5. Extended util::PaymentStatus enum
   - Added PAID status and updated string conversion.
6. Integrated AdminMenu::confirmPayment
   - Validates invoice list, filters by status, allows selection, and confirms payment.
7. Updated CustomerMenu::completePayments
   - Uses parameterized status filtering for invoice selection.
8. Enhanced MenuHelper::selectInvoiceFromUserForPayment
   - Accepts requiredStatus parameter for flexible filtering.
9. Adjusted AdminMenu options
   - Added "Confirm Payment" before Logout.
</Changes>

<Test>
Acceptance Criteria:
1. Admin selects "Confirm Payment" from menu.
   - Verify system prompts and displays invoices filtered by status.
2. Admin selects invoice with status = PAID.
   - Verify payment confirmation updates date, sets status, and sends notification.
3. Admin attempts confirmation with empty invoice list.
   - Verify error message: "No pending invoices available for confirmation."
4. Customer completes payment.
   - Verify selection uses util::PaymentStatus::PENDING and payment flow works correctly.
5. Invalid invoice ID entered.
   - Verify system throws runtime_error with "Payment failed: invalid invoice ID."

Precondition:
1. Admin logged into system.
2. At least one invoice exists in datastore.
3. Notification system available.

Steps:
1. Navigate to Admin menu → Confirm Payment.
2. Select invoice with PAID status.
3. Confirm payment and check notification.
4. Attempt with empty invoice list.
5. Attempt with invalid invoice ID.
</Test>

<Review>
Sreeja Reghukumar
</Review>

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/services/PaymentManagementService.cpp

@@ -368,12 +368,12 @@ void PaymentManagementService::completePayment(const std::string& invoiceID, uti
 	if (invoiceIndex != -1)
 	{
 		Invoice* invoice = currentInvoices.getValueAt(invoiceIndex);
-		if (invoice && invoice->getStatus() != util::PaymentStatus::COMPLETED)
+		if (invoice && invoice->getStatus() != util::PaymentStatus::PAID)
 		{
 			User* currentUser = invoice->getBooking()->getCustomer();
 			invoice->setPaymentMethod(paymentMode);
 			invoice->setPaymentDate(util::Timestamp());
-			invoice->setStatus(util::PaymentStatus::COMPLETED);
+			invoice->setStatus(util::PaymentStatus::PAID);
 			std::string title, message;
 			title = "Payment successful";
 			message = "Payment successful for Invoice ID " + invoiceID;
@@ -384,4 +384,48 @@ void PaymentManagementService::completePayment(const std::string& invoiceID, uti
 	{
 		throw std::runtime_error("Payment failed: invalid invoice ID.");
 	}
+}
+
+/*
+Function: getAllInvoice
+Description: Provides access to all invoices stored in the data store.
+Parameters:
+	- none
+Returns:
+	- util::Map<std::string, Invoice*>&: Map of invoice IDs to invoice objects
+*/
+util::Map<std::string, Invoice*>& PaymentManagementService::getAllInvoices()
+{
+	return m_dataStore.getInvoices();
+}
+
+/*
+Function: confirmPayment
+Description: Confirms payment for a specific invoice. Updates payment date and status,
+			 then sends a notification to the customer.
+Parameters:
+	- invoiceID: std::string, ID of the invoice to confirm
+Returns:
+	- void
+Throws:
+	- std::runtime_error if the invoice ID is invalid
+*/
+void PaymentManagementService::confirmPayment(const std::string& invoiceID)
+{
+	auto& currentInvoices = m_dataStore.getInvoices();
+	int invoiceIndex = currentInvoices.find(invoiceID);
+	if (invoiceIndex == -1)
+	{
+		throw std::runtime_error("Payment confirmation failed: invalid invoice ID.");
+	}
+	Invoice* invoice = currentInvoices.getValueAt(invoiceIndex);
+	if (!invoice || invoice->getStatus() != util::PaymentStatus::PAID)
+	{
+		throw std::runtime_error("Payment confirmation failed: invoice is not awaiting confirmation.");
+	}
+	User* currentUser = invoice->getBooking()->getCustomer();
+	invoice->setStatus(util::PaymentStatus::COMPLETED);
+	std::string title = "Payment Confirmed";
+	std::string message = "Payment Confirmed for Invoice ID " + invoiceID;
+	sendNotification(currentUser, title, message);
 }