I'd like to use the Magento's print feature in my module to have the invoice pdf of a programmatically created order. For that I'd like to get the url that Magento back end uses to print the invoice.
eg : http://localhost/magento1/index.php/admin/sales_order_invoice/print/invoice_id/104/key/eaf550ef39cc92e93b562994019fde14/
My question is how can I get that key to build the url that retrieves the invoice pdf ?