@Override
  protected String getEntitySnapshotFileName() {
    return "system" + File.separator + "users";
  }
All user/role file store in config node's user/role folder. when our system start, we load all
user/role from folder. If we did some alter query, we just store raft log.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/auth/user/LocalFileUserAccessor.java