Information on creating a new processor backend to go with
Business::OnlineThirdPartyPayment.
-----------------------------------------------------------

NOTE: 

    You should read the notes in Business::OnlinePayment first.

Create a subclass of Business::OnlineThirdPartyPayment called
Business::OnlinePayment::(processor name).  You should override at least
the set_defaults, submit, and reference methods.

See Business::OnlineThirdPartyPayment::Interswitchng as an example.

submit: 
  This method functions with both a "Authorize Only" and "Post Authorization"
action.  The former must, at a minumum, ensure that popup_url will return
an appropriate value when submit also sets is_successful.

  Nothing has happened at this point other than verifying the data is valid
and providing the caller with a redirection url.

  When called with "Post Authorization" steps are taken to verify that funds
have been authorized by the processor.

reference:
  This method is called with a hash of key/value pairs, typically as the
result of a HTTP GET or POST, but by whatever mechanism the processor provides.
The return value must be the unique reference provided to the "Authorize Only"
submit.  Since the usage consists of submit(action=>'Authorize Only'),
reference(key=>value...), submit(action=>'Post Authorization'), this may be
the appropriate time to set the state of the object for some processors.