static IndexResolver defaultResolver() {
    return entity -> ContainerNaming.DEFAULT.name(entity).toLowerCase();
  }
Default resolver which uses lower case and simple name of the class: {@code org.MyClass -> myclass}

<p>In elastic, indexes have to be lowercase. From <a href="https://www.elastic.co/guide/en/elasticsearch/guide/current/_document_metadata.html#_index">documentation</a>:
{@code This name must be lowercase, cannot begin with an underscore, and cannot contain commas.}
</p>
criteria/elasticsearch/src/org/immutables/criteria/elasticsearch/IndexResolver.java