curl --request PUT \
  --url https://api.tread-horizon.com/v1/settlements/{settlement-id}/email_settlement \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form email=jsmith@example.com \
  --form pdf='@example-file'

{
  "error": {
    "code": "<string>",
    "error_type": "<string>"
  }
}