Add documentation headers across system modules

Trenser.VehicleServiceSystem/Trenser.VehicleServiceSystem/views/CustomerMenu.cpp

@@ -64,6 +64,14 @@ void CustomerMenu::viewServiceHistory()
 {
 }
 
+/*
+Function: selectInvoiceFromUserForPayment (static helper)
+Description: Lists all pending invoices for the customer and allows selection by index.
+Parameters:
+    - currentInvoices: util::Map<std::string, const Invoice*>&, map of customer invoices
+Returns:
+    - std::string: ID of the selected invoice, or empty string if none selected
+*/
 static std::string selectInvoiceFromUserForPayment(const util::Map<std::string, const Invoice*>& currentInvoices)
 {
     int currentIndex = 1, choice;
@@ -118,6 +126,14 @@ static std::string selectInvoiceFromUserForPayment(const util::Map<std::string,
     }
 }
 
+/*
+Function: selectPaymentMode (static helper)
+Description: Allows the customer to select a payment mode (ONLINE or OFFLINE).
+Parameters:
+    - None
+Returns:
+    - util::PaymentMode: Selected payment mode
+*/
 static util::PaymentMode selectPaymentMode()
 {
     int choice;
@@ -140,6 +156,15 @@ static util::PaymentMode selectPaymentMode()
     }
 }
 
+/*
+Function: completePayments
+Description: Allows the customer to complete pending payments for invoices.
+             Validates invoice selection and payment mode before completing payment.
+Parameters:
+    - None
+Returns:
+    - void
+*/
 void CustomerMenu::completePayments()
 {
 	util::clear();
@@ -155,6 +180,17 @@ void CustomerMenu::completePayments()
     std::cout << "Payment completed successfully.\n";
 }
 
+/*
+Function: displayInvoices (static helper)
+Description: Displays detailed information for all invoices associated with the customer,
+             including booking details, technician, discount, total amount, payment status, and items used.
+Parameters:
+    - currentUserInvoices: util::Map<std::string, const Invoice*>, customer’s invoices
+Returns:
+    - void
+Throws:
+    - std::runtime_error if a null invoice is encountered
+*/
 static void displayInvoices(util::Map<std::string, const Invoice*> currentUserInvoices)
 {
 	if (currentUserInvoices.getSize() == 0)
@@ -206,6 +242,14 @@ static void displayInvoices(util::Map<std::string, const Invoice*> currentUserIn
 	}
 }
 
+/*
+Function: viewInvoices
+Description: Displays invoices associated with the customer by calling displayInvoices.
+Parameters:
+    - None
+Returns:
+    - void
+*/
 void CustomerMenu::viewInvoices()
 {
 	util::clear();