ElasticSearch full support in Jafu and Kofu

[fteychene]

Following #303 and PR #345, Spring-data-elasticsearch weas integrated in Jafu and Kofu, we should support a better integration by :

• Add other configurations for ClientConfiguration
• Add sample for jafu reactive elasticsearch
• Add sample for kofu reactive elasticsearch
• Add sample for kofu coroutime elasticsearch

Bonus point :
We should also try to provide a support for elasticsearch vanilla client like the integration between spring-data r2dbc and r2dbc