docs: check if license key is valid (#32671)

* docs: check if license key is valid

* example actual tests

* comments from pr

* more comments from pr

* proper testing the key expiry

* move closing doc comment

Author: sebastian-alfers

akka-docs/src/main/paradox/general/configuration.md

@@ -64,6 +64,15 @@ If the license key has expired when the `ActorSystem` is started the system will
 The expiry date is exposed by @apidoc[akka.actor.typed.ActorSystem] {scala="#licenseKeyExpiry" java="#getLicenseKeyExpiry"}
 so that you can write a test to remind yourself that it is time for renewal before it has expired.
 
+To verify that your license key is still valid (for example during  CI/CD integration), you can use the following test 
+that will start to fail one month before the license key will expire:
+
+Scala
+: @@snip [ConfigDocSpec.scala](/akka-docs/src/test/scala/docs/config/ConfigDocSpec.scala) { #check-is-key-valid }
+
+Java
+: @@snip [ConfigDocTest.java](/akka-docs/src/test/java/jdocs/config/ConfigDocTest.java) { #check-is-key-valid }
+
 ## When using JarJar, OneJar, Assembly or any jar-bundler
 
 @@@ warning

akka-docs/src/test/java/jdocs/config/ConfigDocTest.java

@@ -14,6 +14,14 @@
 // #imports
 import akka.actor.testkit.typed.javadsl.ActorTestKit;
 
+//#check-is-key-valid
+import java.time.LocalDate;
+import java.util.Optional;
+
+//#check-is-key-valid
+
+import static org.junit.Assert.*;
+
 public class ConfigDocTest {
 
   private Behavior<Void> rootBehavior = Behaviors.empty();
@@ -67,4 +75,18 @@ public ActorSystem createConfiguredSystem() {
     // #custom-config-2
     return system;
   }
+
+  public void compileOnlyIsLicenseKeyValid() {
+    //#check-is-key-valid
+    ActorSystem<Void> system = ActorSystem.create(rootBehavior, "name");
+    Optional<LocalDate> licenseKey = system.getLicenseKeyExpiry();
+
+    assertFalse(licenseKey.isEmpty());
+
+    LocalDate nextMonth = LocalDate.now().plusMonths(1);
+    assertTrue(licenseKey.get().isAfter(nextMonth));
+
+    system.terminate();
+    //#check-is-key-valid
+  }
 }

akka-docs/src/test/scala/docs/config/ConfigDocSpec.scala

@@ -109,4 +109,18 @@ class ConfigDocSpec extends AnyWordSpec with Matchers {
     val system = ActorSystem(rootBehavior, "MySystem", conf)
     ActorTestKit.shutdown(system)
   }
+
+  def compileOnlyIsLicenseKeyValid(): Unit = {
+    //#check-is-key-valid
+    val system = ActorSystem(rootBehavior, "name")
+    val licenseKey = system.licenseKeyExpiry
+    licenseKey.isEmpty shouldBe false
+
+    import java.time.LocalDate
+    val nextMonth = LocalDate.now().plusMonths(1)
+    licenseKey.get.isAfter(nextMonth) shouldBe true
+
+    system.terminate()
+    //#check-is-key-valid
+  }
 }