curl --request POST \
  --url https://analyst.heyhumm.ai/api/upload/presign \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "files": [
    {
      "filename": "<string>",
      "content_type": "<string>",
      "size_bytes": 123
    }
  ]
}
'

{
  "uploads": [
    {
      "filename": "<string>",
      "s3_key": "<string>",
      "presigned_url": "<string>",
      "content_type": "<string>"
    }
  ]
}