RestClientBuilderCustomizer (Spring Boot API)

Functional Interface:
This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface RestClientBuilderCustomizer
```
Callback interface that can be implemented by beans wishing to further customize the RestClient via a RestClientBuilder whilst retaining default auto-configuration.
Since:
2.1.0

- Method Summary
  All Methods Instance Methods Abstract Methods
  Modifier and Type Method Description
  void customize(org.elasticsearch.client.RestClientBuilder builder)
  Customize the RestClientBuilder.

- Method Detail
  - customize
```
void customize(org.elasticsearch.client.RestClientBuilder builder)
```
    Customize the RestClientBuilder.
    Parameters:
    builder - the builder to customize