add support for spring-boot 4x #480

[osoykan]

fixes #480

[Copilot]

Pull Request Overview

This PR adds support for Spring Boot 4.x by creating a new kediatr-spring-boot-4x-starter module, following the same pattern as existing Spring Boot 2x and 3x starters. The implementation mirrors the Spring Boot 3x starter structure with autoconfiguration support.

• Created a new Spring Boot 4x starter module with autoconfiguration
• Updated project settings to include the new starter module
• Removed unused autoconfigure dependency from Spring Boot 3x starter

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
settings.gradle.kts	Added the new kediatr-spring-boot-4x-starter module to the project
gradle/libs.versions.toml	Added Spring Boot 4.0.0 version and related dependency declarations
projects/kediatr-spring-boot-4x-starter/build.gradle.kts	Created build configuration for the 4x starter module
projects/kediatr-spring-boot-4x-starter/src/main/kotlin/com/trendyol/kediatr/spring/KediatRAutoConfiguration.kt	Implemented autoconfiguration for Spring Boot 4x integration
projects/kediatr-spring-boot-4x-starter/src/main/kotlin/com/trendyol/kediatr/spring/KediatRSpringBeanProvider.kt	Implemented Spring bean provider for dependency injection
projects/kediatr-spring-boot-4x-starter/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports	Registered autoconfiguration for Spring Boot 3+ style discovery
projects/kediatr-spring-boot-4x-starter/src/test/kotlin/com/trendyol/kediatr/spring/MediatorTests.kt	Added comprehensive test coverage using shared test cases
projects/kediatr-spring-boot-3x-starter/build.gradle.kts	Removed unused autoconfigure dependency

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[Copilot]

The implementation of getSingleInstanceOf() differs from the Spring Boot 2x and 3x versions, which use the simpler applicationContext.getBean(clazz). This version retrieves bean names, maps them to instances, and calls .single(), which may throw an exception if there are multiple beans of the same type. The 2x/3x approach delegates to Spring's bean resolution logic which properly handles primary beans and qualifiers. Unless there's a specific Spring Boot 4.x compatibility reason for this change, it should be aligned with the existing implementations for consistency.

Suggested change

	override fun <T> getSingleInstanceOf(clazz: Class<T>): T = applicationContext
	.getBeanNamesForType(clazz)
	.map { applicationContext.getBean(it) as T }
	.single()
	override fun <T> getSingleInstanceOf(clazz: Class<T>): T = applicationContext.getBean(clazz)