curl --request POST \
  --url https://api.cartesia.ai/access-token \
  --header 'Cartesia-Version: <cartesia-version>' \
  --header 'Content-Type: application/json' \
  --header 'X-API-Key: <api-key>' \
  --data '{
  "grants": {
    "tts": true,
    "stt": true
  },
  "expires_in": 123
}'

{
  "token": "<string>"
}