Returns a function that uploads a file (by URL or Blob) to the given S3 key(s).
S3 client instance.
(keys, { url?, blob? }) => Promise<string | null> — the download URL on success, or null if no input.
(keys, { url?, blob? }) => Promise<string | null>
null
Returns a function that uploads a file (by URL or Blob) to the given S3 key(s).