feat: Internal invoice generation

- TODO: make use of Stripe invoice

app/controllers/orders_controller.rb

@@ -4,7 +4,7 @@
 # Orders group multiple tickets together for better transaction management
 class OrdersController < ApplicationController
   before_action :authenticate_user!
-  before_action :set_order, only: [ :show, :checkout, :retry_payment, :increment_payment_attempt ]
+  before_action :set_order, only: [ :show, :checkout, :retry_payment, :increment_payment_attempt, :invoice ]
   before_action :set_event, only: [ :new, :create ]
 
   # Display new order form with name collection
@@ -157,6 +157,26 @@ class OrdersController < ApplicationController
     redirect_to checkout_order_path(@order)
   end
 
+  # Display invoice for an order
+  def invoice
+    unless @order.status == "paid" || @order.status == "completed"
+      redirect_to order_path(@order), alert: "La facture n'est disponible qu'après le paiement de la commande"
+      return
+    end
+
+    @tickets = @order.tickets.includes(:ticket_type)
+    
+    # Get the Stripe invoice if it exists
+    begin
+      @stripe_invoice_id = @order.create_stripe_invoice!
+      @stripe_invoice_pdf_url = @order.stripe_invoice_pdf_url if @stripe_invoice_id
+    rescue => e
+      Rails.logger.error "Failed to retrieve or create Stripe invoice for order #{@order.id}: #{e.message}"
+      @stripe_invoice_id = nil
+      @stripe_invoice_pdf_url = nil
+    end
+  end
+
   # Handle successful payment
   def payment_success
     session_id = params[:session_id]