We should also do Validation/Arbitration for one time payments #180
Description
We already have a validation mechanism via an externally configurable contract that enables operators to configure a contract that determines how much is actually paid out to payees on rail settlement (so operators can do things like only pay the payee if they've met the pre-agreed SLAs for example). We should have a similar mechanism for one time payments as well as one time payments are not gated at all right now and are immediately paid out to payees on demand.