@Override
  public Links getLinks() {
    Links links = new Links(getId(), REGION_CONFIG_ENDPOINT);
    links.addLink("indexes", links.getSelf() + "/indexes");
    return links;
  }
this holds the region attributes you can configure using management rest api

for regions created using gfsh but listed using management rest api, the attributes not supported
by management rest api won't be shown.
geode-management/src/main/java/org/apache/geode/management/configuration/Region.java