Transactional saga in Scala II

Part II : Future Imperfect

.. in which Future-based signatures are introduced but the Futures are orchestrated naively 

Now that the problem is understood it's time to consider the second iteration. This time all transactions return Futures. It is very convenient from the perspective of building a reactive service.  Compensation actions still return Tries. Partially for the sake of simplicity, partially to reduce potential for additional errors in the error handling path. The whole saga is wrapped into a Promise to make possible for the client to wait for completion.
As you can see, the conversion to Futures was done rather literally. On the positive side, it's so imperative one can easily see how it works. On the other hand, it looks more like Java. Stay tuned for what I learned during the code review.