feat: add bulk operations methods to admin client

[MarkTripod-Duo]

Description

Added the following two methods to the Admin client module bulk_add_users() bulk_operations()

Also added a new unittest for both methods:

tests/admin/test_bulk.py

Motivation and Context

This change was made in an effort to ensure the highest amount of functional coverage of the Admin API endpoints as possible.

How Has This Been Tested?

Local unittests were run against the updated client library to validate functionality.

Types of Changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [X] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)