Add the ability to customize k8s client config

docs/src/main/asciidoc/kubernetes-client.adoc

@@ -57,10 +57,15 @@ Note that the full list of properties is available in the link:#quarkus-kubernet
 
 In dev mode and when running tests, xref:kubernetes-dev-services.adoc[Dev Services for Kubernetes] automatically starts a Kubernetes API server.
 
-=== Overriding
+=== Customizing and overriding
 
-The extension also allows application code to override either of  `io.fabric8.kubernetes.client.Config` or `io.fabric8.kubernetes.client.KubernetesClient` which are
-normally provided by the extension by simply declaring custom versions of those beans.
+Quarkus provides multiple integration points for influencing the Kubernetes Client provided as a CDI bean.
+
+The first integration point is the use of the `io.quarkus.kubernetes.client.KubernetesConfigCustomizer` interface. When such a bean exists,
+it allows for arbitrary customizations of the `io.fabric8.kubernetes.client.Config` created by Quarkus (which takes into account the `quarkus.kubernetes-client.*` properties).
+
+Alternatively, application code can override the  `io.fabric8.kubernetes.client.Config` or even the `io.fabric8.kubernetes.client.KubernetesClient` bean (which are
+normally provided by the extension) by simply declaring custom versions of those beans.
 
 An example of this can be seen in the following snippet:
 

extensions/kubernetes-client/deployment/pom.xml

@@ -29,6 +29,11 @@
             <groupId>io.quarkus</groupId>
             <artifactId>quarkus-vertx-deployment</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.quarkus</groupId>
+            <artifactId>quarkus-junit5-internal</artifactId>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>

extensions/kubernetes-client/deployment/src/test/java/io/quarkus/kubernetes/client/deployment/KubernetesClientCDITest.java

@@ -0,0 +1,40 @@
+package io.quarkus.kubernetes.client.deployment;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import jakarta.inject.Inject;
+import jakarta.inject.Singleton;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+import io.fabric8.kubernetes.client.Config;
+import io.fabric8.kubernetes.client.KubernetesClient;
+import io.quarkus.kubernetes.client.KubernetesConfigCustomizer;
+import io.quarkus.test.QuarkusUnitTest;
+
+public class KubernetesClientCDITest {
+
+    @Inject
+    KubernetesClient client;
+
+    @Test
+    public void test() {
+        assertEquals("-1", client.getConfiguration().getApiVersion());
+    }
+
+    @RegisterExtension
+    static QuarkusUnitTest runner = new QuarkusUnitTest()
+            .withApplicationRoot((jar) -> jar
+                    .addClasses(Customizer.class))
+            .overrideConfigKey("quarkus.kubernetes-client.devservices.enabled", "false");
+
+    @Singleton
+    public static class Customizer implements KubernetesConfigCustomizer {
+        @Override
+        public void customize(Config config) {
+            config.setApiVersion("-1");
+        }
+    }
+
+}

extensions/kubernetes-client/runtime/src/main/java/io/quarkus/kubernetes/client/KubernetesConfigCustomizer.java

@@ -0,0 +1,25 @@
+package io.quarkus.kubernetes.client;
+
+import java.util.List;
+
+import io.fabric8.kubernetes.client.Config;
+import io.fabric8.kubernetes.client.KubernetesClient;
+import io.quarkus.kubernetes.client.runtime.KubernetesClientBuildConfig;
+import io.quarkus.kubernetes.client.runtime.KubernetesClientProducer;
+import io.quarkus.kubernetes.client.runtime.KubernetesConfigProducer;
+import io.quarkus.runtime.TlsConfig;
+
+/**
+ * Meant to be implemented by a CDI bean that provided arbitrary customization for the default {@link Config} created by
+ * Quarkus.
+ * <p>
+ * The {@link Config} is in turn used to produce the default {@link KubernetesClient}
+ * <p>
+ *
+ * @see KubernetesConfigProducer#config(KubernetesClientBuildConfig, TlsConfig, List) }
+ * @see KubernetesClientProducer#kubernetesClient(Config) }
+ */
+public interface KubernetesConfigCustomizer {
+
+    void customize(Config config);
+}

extensions/kubernetes-client/runtime/src/main/java/io/quarkus/kubernetes/client/runtime/KubernetesConfigProducer.java

@@ -1,10 +1,14 @@
 package io.quarkus.kubernetes.client.runtime;
 
+import java.util.List;
+
 import jakarta.enterprise.inject.Produces;
 import jakarta.inject.Singleton;
 
 import io.fabric8.kubernetes.client.Config;
+import io.quarkus.arc.All;
 import io.quarkus.arc.DefaultBean;
+import io.quarkus.kubernetes.client.KubernetesConfigCustomizer;
 import io.quarkus.runtime.TlsConfig;
 
 @Singleton
@@ -13,7 +17,13 @@ public class KubernetesConfigProducer {
     @DefaultBean
     @Singleton
     @Produces
-    public Config config(KubernetesClientBuildConfig buildConfig, TlsConfig tlsConfig) {
-        return KubernetesClientUtils.createConfig(buildConfig, tlsConfig);
+    public Config config(KubernetesClientBuildConfig buildConfig,
+            TlsConfig tlsConfig,
+            @All List<KubernetesConfigCustomizer> customizers) {
+        var result = KubernetesClientUtils.createConfig(buildConfig, tlsConfig);
+        for (KubernetesConfigCustomizer customizer : customizers) {
+            customizer.customize(result);
+        }
+        return result;
     }
 }