Token expiration handler

Because of the limited lifespan of the accessToken, it's important to handle the situation correctly
when the token expires and needs to be refreshed. To do this, provide tokenHandler for the SDK Builder.

The handler should make a call to your backend, obtain a new access token, and then pass it back to the SDK by returning its value.

val tokenHandler = object : TokenExpirationHandler {
    override fun onTokenExpired(): String? {
        val newToken = ....
        return newToken
TokenExpirationHandler tokenUpdater = () -> {
        String newAccessToken = "...";
        return newAccessToken;



onTokenExpired is called on a non-UI thread.