Add ability to configure TLS certificate and set ApiCompatibilityMode to support ElasticSearch 8

[linghengqian]

• In ElasticSearch 8.x, TLS and user authentication are enabled by default, can the developer suggest how to set http_ca.crt at https://github.com/xpc1024/easy-es-springboot-demo ?

• Here are two blog posts about how to connect via TLS certificate under co.elastic.clients:elasticsearch-java:8.1.1, but it would be better if some friends can give the introduction of global configuration of TLS certificate in easy-es (Maybe in application.yml). Refer to https://www.elastic.co/guide/en/elasticsearch/client/java-api-client/8.1/_encrypted_communication.html and https://spinscale.de/posts/2022-02-17-running-elasticsearch-8-with-testcontainers.html .

• I noticed that the component is using RestHighLevelClient, which means that if somebody need to connect to the ElasticSearch 8.x cluster, he need to add the environment variable ELASTIC_CLIENT_APIVERSIONING: true for ElasticSearch. For this part, please refer to https://www.elastic.co/guide/en/elasticsearch/reference/current/rest-api-compatibility.html . Hope that helps with the corresponding tests.

• As a supplement, developers should try adding a property set to HLRC's client.setApiCompatibilityMode(true) in the easy-es configuration class. See Add API compatibility content-type support to HLRC elastic/elasticsearch#77859, which helps in finding issues with unit tests in Elastic Stack 8.x versions without setting client-side environment variables.

• Also, there is a clarification as https://discuss.elastic.co/t/migration-from-hlrc-to-java-api/300479 , HLRC version 7.17.1 and Java API client 8.x, both use the same RestClient for http communication, and they can coexist in the same project, I think it can be gradually migrated to the new client on easy-es. Of course, the Java API client 8.x is basically generated by the API specification, This leads to the fact that although its API is stable, its documentation is still not finished, and somebody need to go to JavaDoc to see more information.

[xpc1024]

抱歉,8.x版本我们目前暂不支持 未来8.x版本用的人多了我们会考虑支持