Well after looking at the ServiceHandler function I missed that headers needed to be array, so that is fixed (I think). Headers below are the same as passing from api_docs which works. $headers = array(
'Accept: application/json',
'Content-Type: application/json'
);
However problem still exists getting the same error:
**Required field 'id_session' can not be NULL.**
Which leaves me to the format "JSON" string in the arguments. Is that correct? According the code in dr github ServiceHandler if the $payload is json and the $format is undefined it throws an undeclared format exception.
Anyone have any ideas?