Bug 34478: Use op and cud in pay -> paycollect redirect

Bug 34478: Use op and cud in pay -> paycollect redirect

The pay to paycollect post/redirect flow here doesn't actually
consistute a state change, however it's much simpler to add the csrf
token check flow here than to refactor the code to a get (url's quickly
grow too large for a GET) or rework it in other ways.  I opted to do
this for now and work on a refactor at a future date.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>