private CompactionDetails combineListOfDetails(List<CompactionDetails> detailsList) {
    List<LogSegmentName> allSegmentNames = new ArrayList<>();
    for (CompactionDetails details : detailsList) {
      allSegmentNames.addAll(details.getLogSegmentsUnderCompaction());
    }
    return new CompactionDetails(detailsList.get(0).getReferenceTimeMs(), allSegmentNames, null);
  }
Combines a {@link List<CompactionDetails>} into one {@link CompactionDetails} instance. Uses the reference time
of the first entry in the list.
@param detailsList the {@link List<CompactionDetails>} to combine.
@return combines {@code detailsList} into a single {@link CompactionDetails}.
ambry-store/src/test/java/com/github/ambry/store/CompactionLogTest.java