public static AmazonS3Encryption defaultClient() {
        return standard().build();
    }
@return Default client using the {@link com.amazonaws.auth.DefaultAWSCredentialsProviderChain}
and {@link com.amazonaws.regions.DefaultAwsRegionProviderChain} chain
aws-java-sdk-s3/src/main/java/com/amazonaws/services/s3/AmazonS3EncryptionClientBuilder.java