Comment 10 for bug 662912

I've tagged this easy - there are two ways forward:
A: permit the staging librarian to forward to the prod librarian
 - either an unchecked restricted request path (e.g. ask for a restricted file on the private port)
 - or issue tokens from the prod librarian and redirect to there

I think the first option will work best given the current layout of things

B: model which instance the file is in, and have urls and requests generated appropriately. (Also needs token issuing support).