public OAuth2AuthorizationGrantBuilder newTokenConsumer(
            Consumer<? super GrantedOAuth2AccessToken> newTokenConsumer) {
        this.newTokenConsumer = requireNonNull(newTokenConsumer, "newTokenConsumer");
        return this;
    }
Sets an optional hook which gets executed whenever a new token is issued.

<p>This can be used in combination with {@link #fallbackTokenProvider(Supplier)} to store a newly issued
access token which will then be retrieved by invoking the fallback token provider.
oauth2/src/main/java/com/linecorp/armeria/client/auth/oauth2/OAuth2AuthorizationGrantBuilder.java