def create
      @invoice = Invoice.new(params[:invoice])
      @invoice.order_id = @session["order_id"]
      for item_id in params[:invoice_item][:item_id] do
              @invoice.invoice_items << InvoiceItem.new(:item_id => item_id)
      end
      if @invoice.save
         flash[:notice] = ‘Invoice was successfully created.’
         redirect_to :action => ‘list’
      else
         render :action => ‘new’
      end
   end

# Rails inserts the invoice header (the parent)
# Immediately fetches currval(invoices_id_seq) to retrieve the newly created invoice_id
# Uses that invoice_id number and iterates over the invoice_items inserting both the item_id and invoice_id
# commits the results if successful