Add user to impersonate when signing in with Admin user token #1198

Summary

In the REST API is documented that you can impersonate a user using token authentication:

Request Type

New Feature

Type 1: support a REST API:
Yes, this is a supported feature in REST API:
Signing in with server administrator's personal access token(Link opens in a new window) (PAT) to impersonate a user (not available for Tableau Cloud): https://help.tableau.com/current/api/rest_api/en-us/REST/rest_api_ref_authentication.htm#sign_in

Description

Currently, impersonate user is only available for username and password in tableau_auth.py, however it could be needed in other cases where username and password is not available.