code: public static String getQRCode(String name, String issuer, String secret, HmacShaAlgorithm algorithm, String digits, String period) {
          Objects.requireNonNull(name, Required.ACCOUNT_NAME.toString());
          Objects.requireNonNull(secret, Required.SECRET.toString());
          Objects.requireNonNull(issuer, Required.ISSUER.toString());
          Objects.requireNonNull(algorithm, Required.ALGORITHM.toString());
          Objects.requireNonNull(digits, Required.DIGITS.toString());
          Objects.requireNonNull(period, Required.PERIOD.toString());
          
          var buffer = new StringBuilder();
          buffer.append("https://chart.googleapis.com/chart?chs=200x200&cht=qr&chl=200x200&chld=M|0&cht=qr&chl=")
              .append(getOtpauthURL(name, issuer, secret, algorithm, digits, period));
          
          return buffer.toString();
      }
docs: Generates a QR code to share a secret with a user
  
  @param name The name of the account
  @param issuer The name of the issuer
  @param secret The secret to use
  @param algorithm The algorithm to use
  @param digits The number of digits to use
  @param period The period to use
  
  @return An URL to Google charts API with the QR code