Ah ha, the "created" field has been added but doesn't seem to be used
(it doesn't show up in the documentation, but is in the JSON itself).
Adding this property fixed the crashing problem, but actually made the
scheduling stop working as we weren't explicitly setting it in the demo
code and prevented the demo schedule from working.

I removed the property and added the @JSonIgnoreProperties annotation,
which both fixes the crashing and also gets the scheduling working
again.