In making a call to https://ca1.qualtrics.com/API/v3/mailinglists/ML_identity/contacts I am pushing a json string containing extRef. However, I keep getting the following response:
 "httpStatus": "400 - Bad Request",
        "error": {
            "errorMessage": "Unexpected json key provided: extRef",
            "errorCode": "RP_9"
        },
The documentation clearly states extRef is what the field is called. What am I missing here?