I've been following the directions as per https://school.jamfcloud.com/api/docs/#api-Devices-Assign_owner and PUT to https://{yourDomain}.jamfcloud.com/api/devices/:udid/owner with all the relevant information but no matter how I send the request with the user parameter, it returns a code of 400 with the message "UserRequired".
I've spent a whole day trying every variation of submission and multiple programs and methods and the result is the same.
Has anyone got any pointers?