private HttpResponse jsonResponse(QueryResponse response) throws JsonProcessingException {
        return HttpResponse.of(ResponseHeaders.builder(HttpStatus.OK)
                                              .contentType(MediaType.JSON)
                                              .build(), HttpData.ofUtf8(MAPPER.writeValueAsString(response)));
    }
OAP adopt time step by start/end,
reserve step/timeout param to keep consistent with API protocol.
oap-server/server-query-plugin/promql-plugin/src/main/java/org/apache/skywalking/oap/query/promql/handler/PromQLApiHandler.java