Batch creation of users and groups

[hrjn]

It is common for a DSS admin to add multiple users to an instance at once.

The goal here is to provide an example of how to programmatically create users/groups in batches, leveraging DSSClient.create_user() and DSSClient.create_group(). The input can be as simple as a Python list, or it can be a JSON/YAML file.

Bonus:

• in a UIF setup, add impersonation rules with DSSGeneralSettings.add_impersonation_rule()
• grant permissions to existing projects