Initialize PubNub Chat SDK for a Secured Application

Context

You are setting up the PubNub Chat SDK for a web application that requires authenticated access. The application uses PubNub Access Manager, and each user receives an authentication token from your backend server upon login. The backend provides the token as part of the login response.

Task

Write a JavaScript module (chat-init.js) that:

1. Initializes the PubNub Chat SDK with proper configuration
2. Accepts a user ID and an authentication credential from the server
3. Returns the initialized chat instance ready for use
4. Includes comments noting any admin portal prerequisites needed for this to work

Expected Outputs

• A chat-init.js file that exports an async function to initialize and return a Chat SDK instance with authentication support.