Fix User-Agent to use Configuration.VERSION instead of hardcoded string

kubernetes/src/main/java/io/kubernetes/client/openapi/ApiClient.java

@@ -140,7 +140,7 @@ private void init() {
         json = new JSON();
 
         // Set default User-Agent.
-        setUserAgent("Kubernetes Java Client/25.0.0-SNAPSHOT");
+        setUserAgent("Kubernetes Java Client/" + Configuration.VERSION);
 
         authentications = new HashMap<String, Authentication>();
     }

kubernetes/src/test/java/io/kubernetes/client/openapi/ApiClientTest.java

@@ -0,0 +1,48 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+package io.kubernetes.client.openapi;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Collections;
+import okhttp3.Request;
+import org.junit.jupiter.api.Test;
+
+class ApiClientTest {
+
+  @Test
+  void testUserAgentMatchesConfigurationVersion() throws ApiException {
+    ApiClient apiClient = new ApiClient();
+
+    // Build a simple request to verify User-Agent header
+    Request request =
+        apiClient.buildRequest(
+            "http://localhost",
+            "/api/v1/test",
+            "GET",
+            Collections.emptyList(),
+            Collections.emptyList(),
+            null,
+            Collections.emptyMap(),
+            Collections.emptyMap(),
+            Collections.emptyMap(),
+            new String[] {},
+            null);
+
+    // Verify the User-Agent header matches the version from Configuration
+    String expectedUserAgent = "Kubernetes Java Client/" + Configuration.VERSION;
+    String actualUserAgent = request.header("User-Agent");
+
+    assertThat(actualUserAgent).isEqualTo(expectedUserAgent);
+  }
+}