Function s3_put 

pub fn s3_put(
    agent: &Agent,
    bucket: &str,
    key: &str,
    region: &str,
    body: &[u8],
    creds: &UploadCredentials,
) -> Result<String, String>

Upload body bytes to s3://bucket/key using AWS Signature V4.

Returns the full S3 URI (s3://bucket/key) on HTTP 200/201. Any other outcome is an error with a human-readable message. (T-S3-06)