FileSpan addUndeleteEntry(MockId idToUndelete, short lifeVersion) throws StoreException {
    return addUndeleteEntry(idToUndelete, null, lifeVersion);
  }
Adds an undelete entry in the index (real and reference) for {@code idToDelete}.
@param idToUndelete the id to be undeleted.
@param lifeVersion the lifeVersion for undeleted entry.
@return the {@link FileSpan} of the added entries.
@throws StoreException
ambry-store/src/test/java/com/github/ambry/store/CuratedLogIndexState.java