docs: public String signRoomToken(String roomAccess) throws Exception {
          String encodedRoomAcc = UrlSafeBase64.encodeToString(roomAccess);
          byte[] sign = createMac().doFinal(encodedRoomAcc.getBytes());
          String encodedSign = UrlSafeBase64.encodeToString(sign);
          return this.accessKey + ":" + encodedSign + ":" + encodedRoomAcc;
      }