DE-159650: Upgrade Elasticsearch dependency to v9.3.0 and update Docker and phpunit config

[sumitkhopade1986]

Description: Upgrade elasticsearch/elasticsearch dependency from v7 to v9.3.0 and update supporting infrastructure
Possible impact: composer dependencies, Docker ES cluster config, phpunit config, ES version constants

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Summary

• Upgrades elasticsearch/elasticsearch from v7 to v9.3.0 in composer.json
• Updates docker/docker-compose.es.yml to a 2-node ES v9 cluster
• Updates docker/php/Dockerfile PHP version
• Updates phpunit.xml.dist for ES v9 test groups
• Adds ApiVersion::API_VERSION_9 constant to src/ApiVersion.php
• Adds ES v9 version constant to src/ElasticSearchVersion.php
• Removes deprecated src/Elasticsearch/Endpoints/Update.php (no longer needed in v9)

Stacked PRs (1/9)

Base: opensearch → This PR → connection → index-api → client-bulk → secondary-src → tests-bulk → tests-multi-aggregation → tests-transport → tests-remaining

Test Plan

• composer install succeeds with new elasticsearch v9.3.0 dependency
• Docker Compose ES cluster starts correctly with v9 image
• CI phpunit unit tests pass

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Upgrades the project’s Elasticsearch PHP client and related tooling/configuration to support Elasticsearch v9.3.0, including local Docker infrastructure and version constants used across the codebase.

Changes:

• Bumps elasticsearch/elasticsearch requirement to ^9.3 and raises the minimum PHP version to ^8.1 (plus Composer plugin allow-listing).
• Updates local Docker setup to run a 2-node Elasticsearch v9.3.0 cluster and updates the PHP Docker base image.
• Updates PHPUnit configuration schema/coverage configuration and adds v9 constants for API/Elasticsearch version handling.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
composer.json	Updates PHP + Elasticsearch client constraints; adds Composer allow-plugins config.
docker/docker-compose.es.yml	Moves local ES cluster image default to 9.3.0 and adds v9-oriented env config.
docker/php/Dockerfile	Updates local PHP container base image to PHP 8.1.
phpunit.xml.dist	Migrates config to PHPUnit 9.x schema/coverage format.
src/ApiVersion.php	Adds API_VERSION_9 constant.
src/ElasticSearchVersion.php	Adds VERSION_9 constant.
src/Elasticsearch/Endpoints/Update.php	Removes the custom Update endpoint wrapper.

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[Copilot]

Removing src/Elasticsearch/Endpoints/Update.php appears to break the codebase: src/Client.php still imports Elastica\Elasticsearch\Endpoints\Update and instantiates it in Client::updateDocument(). This will lead to a class-not-found/autoload error unless the client code is updated (e.g., to use the upstream Elasticsearch\Endpoints\Update) or the wrapper is kept.

[Copilot]

xsi:noNamespaceSchemaLocation points to the PHPUnit 9.5 schema, but composer.json currently allows PHPUnit ^9.4. If Composer resolves to 9.4.x, XML schema validation can fail or the config may not match the supported elements/attributes. Consider aligning these by either bumping the PHPUnit dev requirement to ^9.5 or using the matching schema URL for the supported PHPUnit version.