add_user supports custom attributes

[deshmukhrajvardhan]

Description

Ability to add custom attributes when creating a user

Motivation and Context

How Has This Been Tested?

Yes, i have screenshots.

1. Using existing api without setting custom attributes

2. Api call succeeds and creates user with custom attribute

3. Api call when custom attribute doesn't exist

4. Incorrect map

Types of Changes

• New feature (non-breaking change which adds functionality)