Function sign_put_request 

pub fn sign_put_request(
    access_key: &str,
    secret_key: &str,
    session_token: &str,
    region: &str,
    bucket: &str,
    key: &str,
    body_sha256: &str,
    amz_date: &str,
    date_stamp: &str,
) -> String

Build the Authorization header value for a PUT to S3.

All inputs are explicit so this function is pure and unit-testable with a fixed timestamp (T-S3-04 golden-value test).

amz_date – "YYYYMMDDTHHmmSSZ" format date_stamp – "YYYYMMDD" format