Cover GitOps friendly Kubernetes additions

Quarkus 3 allows making K8s manifests more Git-friendly [1]
We cover them with these changes, with a single exception[2]

[1] quarkusio/quarkus#31373
[2] quarkusio/quarkus#34673

config/src/main/resources/application.properties

@@ -23,3 +23,9 @@ secrets.app-prop-sha256-handler=${sha256::0e8c2a8b8ecfbd52c3ef17acd44498ee2b892c
 quarkus.kubernetes-client.devservices.enabled=false
 
 quarkus.kubernetes-config.secrets.enabled=true
+
+quarkus.openshift.idempotent=true
+# this variable is relative to the "current directory" and not to the project root
+# see https://github.com/quarkusio/quarkus/blob/main/docs/src/main/asciidoc/deploying-to-kubernetes.adoc?plain=1#L212
+# or https://quarkus.io/guides/deploying-to-kubernetes#generating-idempotent-resources
+# quarkus.kubernetes.output-directory=target/openshift todo https://github.com/quarkusio/quarkus/issues/34673

config/src/test/java/io/quarkus/ts/configmap/api/server/OpenShiftConfigSourcePriorityIT.java

@@ -5,7 +5,17 @@
 import static io.quarkus.ts.configmap.api.server.OpenShiftBaseConfigIT.applyConfig;
 import static java.lang.String.format;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
 
 import jakarta.inject.Inject;
 
@@ -56,6 +66,32 @@ public void testConfigSourcePriorities() {
         assertEquals("side note environment variable", configProperties.sideNote);
     }
 
+    @Test
+    void configIsIdempotent() throws IOException {
+        Predicate<String> containsCommit = line -> line.contains("app.quarkus.io/commit-id");
+        Predicate<String> containsTimestamp = line -> line.contains("app.quarkus.io/build-timestamp");
+
+        // todo change to custom path when https://github.com/quarkusio/quarkus/issues/34673 will be fixed
+        Path folder = app.getServiceFolder().resolve("target/kubernetes").toAbsolutePath();
+        assertTrue(Files.exists(folder), "Folder " + folder + " should exist!");
+
+        List<String> openshift = Files.readAllLines(folder.resolve("openshift.yml"));
+        assertNotEquals(0, openshift.size(), "File openshift.yml should exist and have content!");
+
+        // we do not use idempotent mode for kubernetes, so it should stay as before
+        List<String> kubernetes = Files.readAllLines(folder.resolve("kubernetes.yml"));
+        assertNotEquals(0, kubernetes.size(), "File kubernetes.yml should exist and have content!");
+        assertTrue(kubernetes.stream().anyMatch(containsTimestamp), "File kubernetes.yml should contain timestamps!");
+        assertTrue(kubernetes.stream().anyMatch(containsCommit), "File kubernetes.yml should contain commit ids!");
+
+        // openshift uses idempotent mode
+        List<String> offendingLines = openshift.stream()
+                .filter(containsTimestamp.or(containsCommit))
+                .collect(Collectors.toList());
+        assertEquals(Collections.emptyList(), offendingLines, "Non-idempotent lines found!");
+
+    }
+
     private static void loadConfigSource(Service service) {
         // create Secrets and ConfigMaps
         applyConfig(CONFIGMAP_YAML, openShiftClient);