Unify java versions (#399)

* Unify java versions

* Unify java versions

* Unify java versions

* Unify java versions

Restore Java 17

README.md

@@ -130,7 +130,7 @@ This will generate a GitHub workflow file inside the `.github/workflows` directo
 
 ### Default Testing Strategy
 
-The default testing strategy for ZIO SBT CI plugin is to run `sbt +test` on java 8, 11 and 17. So this will generate the following job:
+The default testing strategy for ZIO SBT CI plugin is to run `sbt +test` on Corretto Java 11, 17 and 21. So this will generate the following job:
 
 ```yaml
 test:

zio-sbt-ci/src/main/scala/zio/sbt/ZioSbtCiPlugin.scala

@@ -56,7 +56,7 @@ object ZioSbtCiPlugin extends AutoPlugin {
       )
     val ciDefaultJavaVersion: SettingKey[String] =
       settingKey[String](
-        "The default Java version which is used in CI, especially for releasing artifacts, defaults to 17"
+        "The default Java version which is used in CI, especially for releasing artifacts, defaults to 17. Note that this is just JDK version used for compilation. Artefact will be compiled with -target and -source flags specified by 'javaPlatform' setting or 'javaPlatform' parameter in 'stdSettings'"
       )
     val ciCheckGithubWorkflow: TaskKey[Unit] = taskKey[Unit]("Make sure if the ci.yml file is up-to-date")
     val ciCheckArtifactsBuildSteps: SettingKey[Seq[Step]] =

zio-sbt-ecosystem/src/main/scala/zio/sbt/ZioSbtEcosystemPlugin.scala

@@ -52,7 +52,7 @@ object ZioSbtEcosystemPlugin extends AutoPlugin {
     lazy val scala213: SettingKey[String]   = settingKey[String]("Scala 2.13 version")
     lazy val zioVersion: SettingKey[String] = settingKey[String]("ZIO version")
 
-    lazy val javaPlatform: SettingKey[String] = settingKey[String]("java target platform, default is 8")
+    lazy val javaPlatform: SettingKey[String] = settingKey[String]("java target platform, default is 11")
 
     val welcomeBannerEnabled: SettingKey[Boolean] =
       settingKey[Boolean]("Indicates whether or not to enable the welcome banner.")
@@ -109,7 +109,7 @@ object ZioSbtEcosystemPlugin extends AutoPlugin {
     scalaVersion       := scala213.value,
     crossScalaVersions := Seq(scala212.value, scala213.value, scala3.value),
     zioVersion         := Versions.zioVersion,
-    javaPlatform       := "8"
+    javaPlatform       := "11"
   )
 
   override def globalSettings: Seq[Def.Setting[_]] =

zio-sbt-githubactions/src/main/scala/zio/sbt/githubactions/ScalaWorkflow.scala

@@ -18,7 +18,7 @@ package zio.sbt.githubactions
 
 import io.circe.syntax._
 
-import zio.sbt.githubactions.ScalaWorkflow.JavaVersion.AdoptJDK18
+import zio.sbt.githubactions.ScalaWorkflow.JavaVersion.JDK11
 
 // The original code of the githubactions package was originally copied from the zio-aws-codegen project:
 // https://github.com/zio/zio-aws/tree/master/zio-aws-codegen/src/main/scala/zio/aws/codegen/githubactions
@@ -217,23 +217,25 @@ object ScalaWorkflow {
 
   case class ScalaVersion(version: String)
 
-  sealed trait JavaVersion {
+  trait JavaVersion {
     val asString: String
   }
   object JavaVersion {
-    case object AdoptJDK18 extends JavaVersion {
-      override val asString: String = "[email protected]"
-    }
-    case object ZuluJDK17 extends JavaVersion {
-      override val asString: String = "[email protected]"
+
+    case class CorrettoJDK(javaVersion: String) extends JavaVersion {
+      override val asString: String = s"corretto:$javaVersion"
     }
+
+    val JDK11: JavaVersion = CorrettoJDK("11")
+    val JDK17: JavaVersion = CorrettoJDK("17")
+    val JDK21: JavaVersion = CorrettoJDK("21")
   }
 
   implicit class JobOps(job: Job) {
     def matrix(
       scalaVersions: Seq[ScalaVersion],
       operatingSystems: Seq[OS] = Seq(OS.UbuntuLatest),
-      javaVersions: Seq[JavaVersion] = Seq(AdoptJDK18)
+      javaVersions: Seq[JavaVersion] = Seq(JDK11)
     ): Job =
       job.copy(
         strategy = Some(