Implement Complete Payments

<UserStory> PAY002: Complete Payments </UserStory>

<Changes>
    1. Integrated Controller with PaymentManagementService to support payment completion workflow.
    2. Implemented PaymentManagementService::completePayment with validation for invoice ID, payment mode, and status update.
    3. Enhanced CustomerMenu with helper functions to display pending invoices in tabular format and allow index-based selection.
    4. Added CustomerMenu::selectPaymentMode to capture payment mode choice (OFFLINE/ONLINE).
    5. Updated CustomerMenu::completePayments to handle invoice selection, payment mode input, and trigger payment completion via Controller.
    6. Implemented notification logic to send confirmation to customers upon successful payment.
</Changes>

<Test>

 Acceptance Criteria:
 1. Payment status marked completed.
 2. Confirmation message shown.
 3. Confirmation notification sent.

 Precondition:
  1. Customer is logged into the system.
  2. At least one pending invoice exists for the customer.
  3. Datastore is available for storing invoices and updating payment status.

 Steps:
  1. Navigate to Customer menu and choose "Complete Payments".
    - Verify that the system lists pending invoices with tabular details.
  2. Select an invoice by index.
    - Verify that the chosen invoice is retrieved correctly.
  3. Enter payment mode (OFFLINE/ONLINE).
    - Verify that the selected mode is applied to the invoice.
  4. Confirm payment completion.
    - Verify that the invoice status changes to COMPLETED.
    - Verify that a confirmation message is displayed.
    - Verify that a notification is sent to the customer.
</Test>

<Review>
Sreeja Reghukumar, please review
</Review>

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

@@ -1,4 +1,6 @@
 #include "Controller.h"
+#include "User.h"
+#include "Invoice.h"
 
 bool Controller::login(const std::string& username, const std::string& password)
 {
@@ -121,11 +123,20 @@ void Controller::removeComboPackage(const std::string& comboPackageID)
 
 util::Map<std::string, const Invoice*> Controller::getInvoicesByUser()
 {
-    return util::Map<std::string, const Invoice*>();
+    User* currentUser = m_authenticationManagementService.getAuthenticatedUser();
+    util::Map<std::string, Invoice*> currentUserInvoices =  m_paymentManagementService.getInvoices(currentUser->getId());
+    util::Map<std::string, const Invoice*> userInvoicesReadOnly;
+    for (int iterator = 0; iterator < currentUserInvoices.getSize(); iterator++)
+    {
+        Invoice* currentInvoice = currentUserInvoices.getValueAt(iterator);
+        userInvoicesReadOnly.insert(currentInvoice->getId(), currentInvoice);
+    }
+    return userInvoicesReadOnly;
 }
 
 void Controller::completePayment(const std::string& invoiceID, util::PaymentMode paymentMode)
 {
+    m_paymentManagementService.completePayment(invoiceID, paymentMode);
 }
 
 util::Vector<const Notification*> Controller::getNotifications()