------------------------
- Use ``boto3`` to fetch on-demand credentials, expanding and standardizing
authorization capabilities. This includes EKS IAM credentials that use
``AssumeRoleWithWebIdentity``.
- Enable opt-in caching of fetched on-demand credentials, to prevent rate
limiting.
- Make the ``pymongo_auth_aws.auth.aws_temp_credentials`` function public
so it can be used in ``pymongocrypt``.