Pluggable MinIO Authorization

[sblack-usu]

Describe the feature you'd like and what it will do
I'd like to implement a POST endpoint that can check S3 authorizations for a user. This can be done through https://min.io/docs/minio/linux/administration/identity-access-management/pluggable-authorization.html#minio-external-access-management-plugin

Why is this feature important?
Instead of syncing hydroshare access control to S3 policies, MinIO may be configured to check with HydroShare if the user has access to a specific resource.

Is your feature request related to a problem? Please describe.
We need a way to check user authorization for direct S3 access. This is a simpler implementation than the previously explored approach of migrating user authorizations from HydroShare to S3 policies.