curl --request PUT \
  --url http://localhost:3001/portal-api/users/{user_id}/custom-attributes/{custom-attribute_id} \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "Value": "true"
}
'

{
  "Value": "true",
  "ID": 1,
  "CustomAttribute": {
    "Name": "Terms of use",
    "Identifier": "terms-of-use",
    "Type": "Boolean",
    "Behaviour": "Edit and view",
    "AddToKeyMetadata": true,
    "Required": true,
    "ShowOnSignUp": true,
    "WriteOnceReadMany": true
  }
}