Add CLI commands to manage users on MLFlow server via REST API

[matbun]

Add CLI commands to manage users on MLFlow server via REST API: https://mlflow.org/docs/latest/auth/index.html#

Unfortunately, MLFlow server does not provide an admin control panel, thus user management can be done exclusively through REST API.

Commands needed:

• Create new user
• Create new experiment
• Create new model
• Add user to experiment (or list of experiments)
• Parse a CSV with fields user, experiment, permission fields, and add those users to the given experiments with given permissions, creating users and experiments if they don't exist.

Unfortunately it is not possible at the moment to list all users registered in the MLFlow server.