JSONSerializer settings not honored

[Mortana89]

When specifying a JSONSerializer with typenamehandling 'Auto', we get cryptic error messages about bad requests.
Understood from another issue, this is due to the fact that the bulkexecutor uses it's own translator under the hood.
However, when we have abstract nested classes, we save the typename in the database to make sure we can handle the (de)serialization correctly.
Without being able to specify this in the bulk executor, it omits the $type property and as such these objects fail to deserialize...