curl --request POST \
  --url https://api.cartesia.ai/agents/phone-numbers/providers \
  --header 'Authorization: Bearer <token>' \
  --header 'Cartesia-Version: <cartesia-version>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "type": "twilio",
  "account_sid": "<string>",
  "api_key_sid": "<string>",
  "api_key_secret": "<string>",
  "region": "us1"
}
'

{
  "type": "twilio",
  "id": "<string>",
  "account_sid": "<string>",
  "api_key_sid": "<string>",
  "region": "us1"
}