public MultiPartStreamer addFile(String name, Path path) {
        String type = Exceptions.uncheck(() -> Files.probeContentType(path));
        return addData(name, type != null ? type : "application/octet-stream", path.getFileName().toString(), () -> asStream(path));
    }
Adds the contents of the file at the given path as a named part in this.
hosted-api/src/main/java/ai/vespa/hosted/api/MultiPartStreamer.java