fix: reuse HttpClient instance across authorize() calls

[vikshab]

Fixes #142 issue

Problem

Each call to OpaAuthorizer.authorize() creates a new HttpClient via HttpClient.newHttpClient(). Every HttpClient spawns a SelectorManager background thread and its own connection pool that are never shut down, causing unbounded thread growth under load.

Fix

Move HttpClient to an instance field initialized once in the constructor. HttpClient is thread-safe and designed to be reused — a single instance handles all concurrent requests via its internal connection pool, eliminating the thread leak

[stackable-cla]

All committers have signed the CLA.

[maltesander]

Hi @vikshab,

thank you, LGTM, would you mind adding a changelog entry under "unreleased" and a new section "### Fixed" ?

druid-opa-authorizer/CHANGELOG.md

Line 9 in 31a6568

I can do it as well.

Malte

[vikshab]

Hi @vikshab,

thank you, LGTM, would you mind adding a changelog entry under "unreleased" and a new section "### Fixed" ?

druid-opa-authorizer/CHANGELOG.md

Line 9 in 31a6568

I can do it as well.

Malte

@maltesander Pushed new commit

[maltesander]

Hey thank you, but this is in the wrong place. I meant something like this (from the top):

# Changelog

## [Unreleased]

### Added

- Add support for Druid 35.0.1 ([#138]).
- Add support for Druid 34.0.0 (deprecated) ([#134], [#138]).

### Fixed

- Reuse HttpClient instance across authorize() calls ([#143]).

### Removed

- Remove support for Druid 33.0.0 ([#138]).
- Remove support for Druid 31.0.1 ([#134]).

[#134]: https://github.com/stackabletech/druid-opa-authorizer/pull/134
[#138]: https://github.com/stackabletech/druid-opa-authorizer/pull/138
[#143]: https://github.com/stackabletech/druid-opa-authorizer/pull/143