Add actions to support user management in MinIO

[Barteus]

It would be nice to allow using actions to manage users in the MinIO. Now the only option is to use the console (UI) or mc (CLI).

Supported actions should be based on upstream documentation: https://docs.min.io/docs/minio-multi-user-quickstart-guide.html

After the CRUD operations are implemented, then integration test covering these actions should be created. Users created this way should be able to access data in both server and gateway mode.