docs: private static String slurpUtf8Part(HttpServletRequest request, HttpServletResponse response, String name, int maxLength)
              throws IOException, ServletException
      {
          Part part = request.getPart(name);
          if (part == null) {
              response.sendError(400, "Form field " + jq(name) + " is missing");
              return null;
          }
  
          byte[] bytes = new byte[maxLength];
          InputStream in = part.getInputStream();
          int bytesRead = in.read(bytes);
  
          if (bytesRead == -1) {
              return "";
          }
  
          String s = StringUtil.utf8ToString(bytes, 0, bytesRead);
  
          if (in.read() != -1) {
              response.sendError(400, "Field " + jq(name) + " is too long (the limit is " + maxLength + " bytes): " + jq(s));
              return null;
          }
  
          // TODO: We're just assuming the content is UTF-8 text.  We should actually check it.
          return s;
      }