private String join(Set<String> set) {
        StringBuilder joined = new StringBuilder();
        String delim = ""; //$NON-NLS-1$

        for (String s : set) {
            joined.append(delim);
            joined.append(s);
            delim = ", "; //$NON-NLS-1$
        }

        return joined.toString();
    }
@return if the request is simple, as defined by CORS spec
plugins/cors-policy/src/main/java/io/apiman/plugins/cors_policy/CorsConnector.java