pad timeseries data window by aggregation window

  from_ = from;

  until_ = until;

  auto from_with_padding = from.unixMicros();

  if (aggr_fn != AggregationFunction::kNoAggregation) {

    if (from_with_padding > aggr_window.microseconds()) {

      from_with_padding -= aggr_window.microseconds();

    }

  }

  metric_service->scanSamples(

      metric_key,

      from,

      DateTime(from_with_padding),

      until,

      [this] (Sample* sample) -> bool {

        processSample(sample, false);