Merged PR 1150: Implement Confirm Payment Functionality

Implement Confirm Payment Functionality

- Added Controller::getAllInvoices – retrieves all invoices from PaymentManagementService and returns them as a read-only map
- Implemented Controller::confirmPayment – delegates payment confirmation for a given invoice ID to PaymentManagementService
- Introduced PaymentManagementService::getAllInvoice – provides access to all invoices stored in the datastore
- Added PaymentManagementService::confirmPayment – confirms payment for a specific invoice, updates payment date and status, and sends notification
- Extended util::PaymentStatus enum – added PAID status and updated string conversion
- Integrated AdminMenu::confirmPayment – validates invoice list, filters by status, allows selection, and confirms payment
- Updated CustomerMenu::completePayments – uses parameterized status filtering for invoice selection
- Enhanced MenuHelper::selectInvoiceFromUserForPayment – accepts requiredStatus parameter for flexible filtering
- Adjusted AdminMenu options – added "Confirm Payment" before Logout

Related work items: #1797

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/utilities/Validator.cpp

@@ -116,13 +116,15 @@ bool util::isPasswordValid(const std::string& password)
  *     usersMap - map of user objects keyed by identifier
  * Returns:
  *     bool - true if the username is already in use by an active user, false otherwise
+ * Notes:
+ *     - Only considers users with state util::State::ACTIVE
  */
 bool util::isUsernameDuplicate(const std::string& username, const util::Map<std::string, User*>& usersMap)
 {
     int index = usersMap.findIf(
         [&](const std::string&, User* user)
         {
-            return (user->getUserName() == username);
+            return (user->getUserName() == username && user->getState() == util::State::ACTIVE);
         }
     );
     return index != -1;