private ClientConfiguration resolveClientConfiguration() {
        return (clientConfig == null) ? clientConfigFactory.getConfig() :
                new ClientConfiguration(clientConfig);
    }
If not explicit client configuration is provided we consult the {@link
ClientConfigurationFactory} of the service. If an explicit configuration is provided we use
ClientConfiguration's copy constructor to avoid mutation.
aws-java-sdk-core/src/main/java/com/amazonaws/client/builder/AwsClientBuilder.java