String lenientSearch(List<String> indices, @Nullable String type) {
    return '/' + String.join(",", indices) +
      "/_search?allow_no_indices=true&expand_wildcards=open&ignore_unavailable=true";
  }
Matches the behavior of {@code IndicesOptions#lenientExpandOpen()}
zipkin-storage/elasticsearch/src/main/java/zipkin2/elasticsearch/internal/client/SearchCallFactory.java