code: public boolean isText() {
          boolean isJson = contentType.map(contentType -> "application/json".equals(contentType)).orElse(false);
          boolean isPlainText = contentType.map(contentType -> "text/plain".equals(contentType)).orElse(false);
  
          return charset.isPresent() || isJson || isPlainText;
      }
docs: Whether this message protocol is a text based protocol.
  
  This is determined by whether the charset is defined.
  
  @return true if this message protocol is text based.