feat(java-sdk)!: support server-side batch check endpoint

[piotrooo]

Description

Caution

Breaking Change! This change renames the existing batchCheck method (which calls the /check API in parallel) to clientBatchCheck.
If you would like to continue to use the client-side batch check, replace your calls to batchCheck with clientBatchCheck, and reference the results using the result property (formerly was responses).

Implemented a server-side batch check API, as @jimmyjames mentioned here.

References

Review Checklist

• I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected