createdAt will be updated on upsert (updateOrCreate) call

[0ff]

There is a quirk in this mixin: if you upsert a model (i.e. you just know the id and properties, but you don't want to find it first) the createdAt-Timestamp is updated, too. This must not happen, of course.
I fear it's related to the lb-ds-juggler's implementation of default values.

Can you think of a solution besides querying for the model everytime?

See PR #10 for a breaking test. I'm not even sure if this can be fixed in the mixin. If not, it should at least be clearly stated in the readme.

[xixilive]

It should ENFORCE unset createdAt property before any update operation.