code: public MessageBuilder addAttachmentAsSpoiler(InputStream stream, String fileName) {
          delegate.addAttachment(stream, "SPOILER_" + fileName);
          return this;
      }
docs: Adds an attachment to the message and marks it as spoiler.
  
  @param stream The stream of the file.
  @param fileName The name of the file.
  @return The current instance in order to chain call methods.