[backend] Update dependency co.elastic.clients:elasticsearch-java to v9 (release/current)

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
co.elastic.clients:elasticsearch-java	8.18.0 -> 9.0.0

---

Warning

Some dependencies could not be looked up. Check the Dependency Dashboard for more information.

---

Release Notes

elastic/elasticsearch-java (co.elastic.clients:elasticsearch-java)

v9.0.0

Compare Source

What's Changed

Check the official release notes - in particular the breaking changes! Also we have a new Reference page.
A migration guide from version 8.x to 9.x of the client will be published soon to make the upgrade process easier.
The easiest way to setup the new 9.0.0 client is to use the new builder, as explained in the new docs:

ElasticsearchClient esClient = ElasticsearchClient.of(b -> b
    .host(serverUrl)
    .apiKey(apiKey)
);

Otherwise to keep using the old builder and the legacy RestClient, the elasticsearch-rest-client dependency has to be added to the project:

// gradle
implementation("org.elasticsearch.client:elasticsearch-rest-client:9.0.0")

<!--maven-->
<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>elasticsearch-rest-client</artifactId>
    <version>9.0.0</version>
</dependency>

Full Changelog: elastic/elasticsearch-java@v8.18.0...v9.0.0

---

Configuration

📅 Schedule: Branch creation - "after 10pm every weekday,every weekend,before 5am every weekday" (UTC), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.