GH-3731: Upgrade Gradle and configure Java/Kotlin toolchains

Fixes: #3731

* Upgrade Gradle wrapper from 8.9 to 8.12.1
* Configure Java toolchain to use Java 23
* Add Kotlin compiler options for test compilation
* Simplify project inclusion in settings.gradle using directory scan

Signed-off-by: Soby Chacko <soby.chacko@broadcom.com>

build.gradle

@@ -131,6 +131,9 @@ configure(javaProjects) { subproject ->
 	apply from: "${rootProject.projectDir}/gradle/publish-maven.gradle"
 
 	java {
+		toolchain {
+			languageVersion = JavaLanguageVersion.of(23)
+		}
 		withJavadocJar()
 		withSourcesJar()
 		registerFeature('optional') {
@@ -148,6 +151,16 @@ configure(javaProjects) { subproject ->
 		options.encoding = 'UTF-8'
 	}
 
+	compileTestKotlin {
+		kotlinOptions {
+			jvmTarget = JavaVersion.VERSION_17
+		}
+		compilerOptions {
+			allWarningsAsErrors = true
+		}
+	}
+
+
 	eclipse.project.natures += 'org.springframework.ide.eclipse.core.springnature'
 
 	// dependencies that are common across all java projects

gradle.properties

@@ -3,3 +3,4 @@ org.gradle.jvmargs=-Xmx1536M -Dfile.encoding=UTF-8
 org.gradle.caching=true
 org.gradle.parallel=true
 kotlin.stdlib.default.dependency=false
+#kotlin.jvm.target.validation.mode = IGNORE

gradle/wrapper/gradle-wrapper.properties

@@ -1,7 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionSha256Sum=d725d707bfabd4dfdc958c624003b3c80accc03f7037b5122c4b1d0ef15cecab
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.9-bin.zip
+distributionSha256Sum=8d97a97984f6cbd2b85fe4c60a743440a347544bf18818048e611f5288d46c94
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.12.1-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME

settings.gradle

@@ -11,7 +11,8 @@ plugins {
 
 rootProject.name = 'spring-kafka-dist'
 
-include 'spring-kafka'
-include 'spring-kafka-bom'
-include 'spring-kafka-test'
-include 'spring-kafka-docs'
+rootDir.eachDir { dir ->
+	if (dir.name.startsWith('spring-')) {
+		include ":${dir.name}"
+	}
+}