curl --request POST \
  --url https://api.example.com/v1/voices/add \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form 'name=<string>' \
  --form 'description=<string>' \
  --form 'files=<string>' \
  --form files.items='@example-file'

{
  "user_id": "<string>",
  "voice_id": "<string>",
  "name": "<string>",
  "description": "",
  "created_at": 123,
  "updated_at": 123
}