code: public static HttpResponse fromStream(Stream<? extends ServerSentEvent> contentStream,
                                            Executor executor) {
          return fromStream(defaultHttpHeaders, contentStream, HttpHeaders.EMPTY_HEADERS, executor);
      }
docs: Creates a new Server-Sent Events stream from the specified {@link Stream}.
  
  @param contentStream the {@link Stream} which publishes the objects supposed to send as contents
  @param executor the executor which iterates the stream