curl --request POST \
  --url https://api.sentvia.ai/v1/messages/{id}/reply \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "text": "<string>",
  "html": "<string>",
  "reply_all": true
}
'

{
  "id": "<string>",
  "thread_id": "<string>",
  "message_id": "<string>",
  "ses_message_id": "<string>",
  "idempotent": true
}