byte[] getBytes() {
            if (messageContents == null) {
                buildMessage();
            }
            if (messageContents.length > currentOutputPosition) {
                final byte[] tmp = new byte[currentOutputPosition];
                System.arraycopy( messageContents, 0, tmp, 0, currentOutputPosition );
                messageContents = tmp;
            }
            return messageContents;
        }
Returns the response that has been generated after shrinking the
array if required and base64 encodes the response.

@return The response as above.
httpclient5/src/main/java/org/apache/hc/client5/http/impl/auth/NTLMEngineImpl.java