private static Publisher<? extends BodyPart> partsPublisher(String boundary, byte[] data,
                                                                AtomicLong totalCount) {
        return partsPublisher(boundary, ImmutableList.of(data), totalCount);
    }
Create the parts publisher for the specified boundary and request chunk.
@param boundary multipart boundary string
@param data data for the chunk
@return publisher of body parts
core/src/test/java/com/linecorp/armeria/common/multipart/MultipartDecoderTest.java