curl --request POST \
  --url https://api.example.com/partner/instances/users/create \
  --header 'Content-Type: application/x-www-form-urlencoded' \
  --data 'instance_id=<string>' \
  --data 'username=<string>' \
  --data 'first_name=<string>' \
  --data 'last_name=<string>'

{
  "id": "<string>",
  "username": "<string>",
  "first_name": "<string>",
  "last_name": "<string>",
  "enabled": "<string>",
  "instance_id": "<string>"
}