Oh boy...
I could have had that quicker. I never tried to put it non-serialized in the request-body and was convinced that it had something to do with the new construction of maps.
But I would actually consider that a groundbreaking change, because if the request-body receives already serialized data, it arrives incorrectly at the endpoint.
You wrote that it could have been better documented. I have just searched in vain for a reference to these changes.
I would like to suggest that this be included in the changelogs or displayed more prominently there.
Anyway, thanks Christian for the clarification. It saves me a lot of trouble.
Beste regards, Andreas