put https://customer.my.onetrust.com/api/datasubject/v2/requestqueues//customfields/
Use this API to add/update the custom fields of a request using its requestQueueRefId in the language specified.
Example Request
PUT https://{hostname}/api/datasubject/v2/requestqueues/{requestQueueRefId}/customfields/{language}
PUT https://trial.onetrust.com/api/datasubject/v2/requestqueues/SL244HWD6D/customfields/en-us