Document the returned token from IMS

Ah, and the auth() call does not return the token. Rather it returns a token information object which contains the access token:
```Object {token_type: "bearer", access_token: "xxx…", expires_in: 86399993}```
Thus, I need to extract tokenInfo.access_token to make an API call. This was not clear in the docs.

Start at the auth() documentation and check how its return value is currently described. Update the docs to show that auth() returns a token information object and explain extracting access_token for an API call; done when the returned shape and extraction are clear.

Written by the indexing model from the issue text.