static ByteArrayBuffer encode(
            final Charset charset, final CharSequence string) {
        final ByteBuffer encoded = charset.encode(CharBuffer.wrap(string));
        final ByteArrayBuffer bab = new ByteArrayBuffer(encoded.remaining());
        bab.append(encoded.array(), encoded.arrayOffset() + encoded.position(), encoded.remaining());
        return bab;
    }
The epilogue to be included after the multipart content.
httpclient5/src/main/java/org/apache/hc/client5/http/entity/mime/AbstractMultipartFormat.java