Upgrade to Gradle 9.3.0

[Copilot]

Gradle 9 removed LenientConfiguration.getFiles() API used by Spring Boot 2.x plugin. Spring Boot 3.x requires Java 17+, incompatible with Java 8 smoke test containers.

Changes

Gradle updates

• Wrapper: 8.14.3 → 9.3.0
• protobuf-gradle-plugin: 0.8.19 → 0.9.6

Smoke test JAR packaging

Replaced Spring Boot plugin with Shadow plugin in ai.smoke-test-jar.gradle.kts:

tasks.named<ShadowJar>("shadowJar") {
  mergeServiceFiles()
  
  transform(PropertiesFileTransformer::class.java) {
    paths = listOf("META-INF/spring.factories")
    mergeStrategy = "append"
  }
  
  manifest {
    attributes["Main-Class"] = project.findProperty("mainClassName") 
      ?: "com.microsoft.applicationinsights.smoketestapp.SpringBootApp"
  }
}

tasks.named<Jar>("jar") {
  enabled = false  // Prevent overwriting shadowJar output
}

Critical: Shadow's append() method concatenates files creating duplicate property keys. Spring Boot reads only first occurrence:

# Broken - duplicate keys
org.springframework.boot.autoconfigure.EnableAutoConfiguration=ActuatorConfigs...
org.springframework.boot.autoconfigure.EnableAutoConfiguration=WebMvcConfigs...

# Fixed - merged values  
org.springframework.boot.autoconfigure.EnableAutoConfiguration=ActuatorConfigs...,WebMvcConfigs...

PropertiesFileTransformer merges duplicate keys into comma-separated values, enabling all auto-configurations (ServletWebServerFactory, WebMvcMetricsAutoConfiguration, etc.).

App-specific fixes

• JettyNativeHandler, ReadOnly: Custom main class via ext.set("mainClassName", "...")
• DiagnosticExtension: MockExtension → compileOnly (prevents classloader conflict when extension loaded separately as agent extension)
• NonDaemonThreads: Added spring-boot-loader dependency (TestController requires JarLauncher class to locate JAR)

Original prompt

Upgrade the project to Gradle 9

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