Add the ability to customize k8s client config

This gives users the ability to alter the
configuration provided by Quarkus in arbitrary ways

The pattern implemented is exactly the same as the
one used in other extensions

Relates to: #31395

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 +1,39 @@
+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));
+
+    @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;
     }
 }