The code example for creating a OAuth2ClientHttpRequestInterceptor is incorrect in Access Protected Resources for the Current User. The example:

OAuth2ClientHttpRequestInterceptor requestInterceptor =
        new OAuth2ClientHttpRequestInterceptor(authorizedClientManager, clientRegistrationIdResolver());
return RestClient.builder()
        .requestInterceptor(requestInterceptor)
        .build();

should instead be:

OAuth2ClientHttpRequestInterceptor requestInterceptor =
        new OAuth2ClientHttpRequestInterceptor(authorizedClientManager);
requestInterceptor.setClientRegistrationIdResolver(clientRegistrationIdResolver());

return RestClient.builder()
        .requestInterceptor(requestInterceptor)
        .build();