code: public Result propagateHeaders(ClientRequest request, final HttpServerExchange exchange) {
          String tid = exchange.getRequestHeaders().getFirst(HttpStringConstants.TRACEABILITY_ID);
          String token = exchange.getRequestHeaders().getFirst(Headers.AUTHORIZATION);
          String cid = exchange.getRequestHeaders().getFirst(HttpStringConstants.CORRELATION_ID);
          return populateHeader(request, token, cid, tid);
      }
docs: Support API to API calls with scope token. The token is the original token from consumer and
  the client credentials token of caller API is added from cache.
  
  This method is used in API to API call
  
  @param request the http request
  @param exchange the http server exchange