Qiscus SDK provide Client Authentication called `setUser`, you can use this method to login or register user when unavailable.
Qiscus Web SDK : https://documentation.qiscus.com/chat-sdk-javascript/authentications
Qiscus Android SDK : https://documentation.qiscus.com/chat-sdk-android/authentications
Qiscus iOS SDK : https://documentation.qiscus.com/chat-sdk-ios/authentications
Qiscus Flutter SDK: https://documentation.qiscus.com/chat-sdk-flutter/authentications
Qiscus Rest API : https://documentation.qiscus.com/chat-server-api/user#login-or-register
You also can create user via Dashboard under Users page. Read details about Identity Management on this blog post.