Upload an object (raw body or multipart 'file')

{
  "bucket": "avatars",
  "key": "ada.png",
  "size": 20480,
  "content_type": "image/png",
  "etag": "9b2cf535f27731c974343645a3985328",
  "url": "https://api.example.com/storage/v1/files/production/avatars/ada.png"
}