Bump Kotlin API and language version to 2.1

Author: marcphilipp

gradle/plugins/common/src/main/kotlin/junitbuild.kotlin-library-conventions.gradle.kts

@@ -1,5 +1,5 @@
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
-import org.jetbrains.kotlin.gradle.dsl.KotlinVersion
+import org.jetbrains.kotlin.gradle.dsl.KotlinVersion.KOTLIN_2_1
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 plugins {
@@ -16,7 +16,7 @@ val javaLibraryExtension = project.the<JavaLibraryExtension>()
 tasks.withType<KotlinCompile>().configureEach {
 	compilerOptions {
 		jvmTarget = javaLibraryExtension.mainJavaVersion.map { JvmTarget.fromTarget(it.toString()) }
-		apiVersion = KotlinVersion.fromVersion("1.6")
+		apiVersion = KOTLIN_2_1
 		languageVersion = apiVersion
 		allWarningsAsErrors.convention(true)
 		javaParameters = true

junit-jupiter-api/junit-jupiter-api.gradle.kts

@@ -23,6 +23,10 @@ dependencies {
 }
 
 tasks {
+	compileKotlin {
+		// https://github.com/junit-team/junit5/issues/4371
+		compilerOptions.allWarningsAsErrors = false
+	}
 	jar {
 		bundle {
 			val version = project.version

platform-tooling-support-tests/projects/gradle-kotlin-extensions/build.gradle.kts

@@ -27,8 +27,8 @@ java {
 tasks.withType<KotlinCompile>().configureEach {
 	kotlinOptions {
 		jvmTarget = "17"
-		apiVersion = "1.6"
-		languageVersion = "1.6"
+		apiVersion = "2.1"
+		languageVersion = "2.1"
 	}
 }