curl --request POST \
  --url https://api.x.com/2/chat/media/upload/initialize \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "conversation_id": "1603419216513746946:1603419216513746946",
  "total_bytes": 1
}
'

{
  "data": {
    "conversation_id": "1603419216513746946:1603419216513746946",
    "media_hash_key": "rByqeHiVlD",
    "session_id": "735401"
  }
}