Test subscription to events produced by EventReactor

[alexander-yevsyukov]

This PR adds the test to check the statement from the issue #1210. Related tests were converted to Kotlin for better readability.

Other notable changes

• Minor improvements to documentation layout.
• Added missing annotations and remove wrong ones.
• Gradle was bumped to 9.2.0.

[Copilot]

Pull Request Overview

This PR enhances event generation capabilities by adding support for event reactors in the test infrastructure and improving documentation. It introduces a new test case demonstrating event subscription from EventReactor components, along with supporting test fixtures including a new aggregate, reaction, and commands/events for password management.

Key changes:

• Added test infrastructure for password change handling with UserAccountAggregate and PasswordChangeReaction
• Introduced new test case subscribe to events produced by 'EventReactor'
• Refactored test organization by migrating classes to appropriate packages
• Updated Gradle wrapper to version 9.2.0

Reviewed Changes

Copilot reviewed 26 out of 27 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
version.gradle.kts	Bumped snapshot version to 352
pom.xml	Updated version reference to match new snapshot
gradle/wrapper/gradle-wrapper.properties	Upgraded Gradle wrapper to 9.2.0
server/src/testFixtures/proto/spine/test/client/users/*.proto	Added password field and new events/commands for password management
server/src/testFixtures/kotlin/io/spine/test/client/users/*.kt	Added UserAccountAggregate, PasswordChangeReaction, and Context builder
server/src/testFixtures/java/io/spine/test/client/users/*.java	Created package-info and moved LoginProcess to users package
server/src/testFixtures/java/io/spine/test/client/*.java	Refactored to use centralized Context builder
server/src/test/java/io/spine/client/ClientSubscriptionsSpec.kt	Converted test from Java to Kotlin and added EventReactor test case
server/src/main/java/io/spine/server/stand/Stand.java	Enhanced documentation and added nullness annotations
server/src/main/java/io/spine/server/tenant/TenantAware.java	Removed redundant @nonnull annotation
server/src/main/java/io/spine/server/stand/TenantSubscriptionRegistry.java	Replaced @nullable with var for local variables
client/src/main/java/io/spine/client/SubscriptionRequest.java	Improved documentation clarity
gradlew/gradlew.bat	Removed unused CLASSPATH variable
core/src/main/proto/spine/core/diagnostics.proto	Reordered documentation for better readability