AWS SDK for Rust will log AWS credentials when TRACE-level logging is enabled for request sending

aws-sigv4 is a rust library for low level request signing in the aws cloud platform. The `aws_sigv4::SigningParams` struct had a derived `Debug` implementation. When debug-formatted, it would include a user's AWS access key, AWS secret key, and security token in plaintext. When TRACE-level logging is enabled for an SDK, `SigningParams` is printed, thereby revealing those credentials to anyone with access to logs. All users of the AWS SDK for Rust who enabled TRACE-level logging, either globally (e.g. `RUST_LOG=trace`), or for the `aws-sigv4` crate specifically are affected. This issue has been addressed in a set of new releases. Users are advised to upgrade. Users unable to upgrade should disable TRACE-level logging for AWS Rust SDK crates.