Add gradle9 module: Spring Boot 4 build migrated from Gradle 8 to Gradle 9

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Gth99spB1CzQmBFofXmU4Z

gradle9/after/build.gradle.kts

@@ -0,0 +1,35 @@
+plugins {
+    java
+    alias(libs.plugins.spring.boot)
+    alias(libs.plugins.dependency.management)
+}
+
+group = "com.ankurm"
+version = "0.0.1"
+
+tasks.withType<JavaCompile>().configureEach { options.release = 17 }
+
+base { archivesName = "g9demo" }
+
+repositories { mavenCentral() }
+
+dependencies {
+    implementation(libs.starter.webmvc)
+    testImplementation(libs.starter.webmvc.test)
+}
+
+// Configuration-cache-safe: a typed task whose inputs are Property/Provider values,
+// so nothing reaches back into the script or Project when the task executes.
+abstract class BuildInfo : DefaultTask() {
+    @get:Input abstract val text: Property<String>
+    @get:OutputFile abstract val target: RegularFileProperty
+    @TaskAction fun write() { target.get().asFile.writeText(text.get()) }
+}
+
+tasks.register<BuildInfo>("buildInfo") {
+    val prefix = "${project.name} ${project.version} "          // read at configuration time
+    text = providers.environmentVariable("BUILD_STAMP").orElse("local").map { "$prefix$it\n" }
+    target = layout.buildDirectory.file("build-info.txt")
+}
+
+tasks.named<Test>("test") { useJUnitPlatform() }