code: private String getCookieValue(HttpServerExchange exchange, String cookieName) {
          String value = null;
          Map<String, Cookie> requestCookies = exchange.getRequestCookies();
          if (requestCookies != null) {
              Cookie cookie = exchange.getRequestCookies().get(cookieName);
              if (cookie != null) {
                  value = cookie.getValue();
              }  
          }
  
          return value;
      }
docs: Retrieves the value of a cookie with a given name from a HttpServerExchange
  
  @param exchange The exchange containing the cookie
  @param cookieName The name of the cookie
  
  @return The value of the cookie or null if none found