MINOR: add lower case lister name integration test (#19932)

In [KIP-1143](https://cwiki.apache.org/confluence/x/LwqWF), it
deprecated Endpoint#listenerName and removed
org.apache.kafka.network.EndPoint. Certain parts of the code depend on
listener name normalization. We should add a test to make sure there is
no regression.

Followup: 
https: //github.com/apache/kafka/pull/19191#issuecomment-2939855317
Reviewers: Chia-Ping Tsai <chia7712@gmail.com>

core/src/test/scala/integration/kafka/server/KRaftClusterTest.scala

@@ -43,7 +43,7 @@ import org.apache.kafka.metadata.bootstrap.BootstrapMetadata
 import org.apache.kafka.network.SocketServerConfigs
 import org.apache.kafka.server.authorizer._
 import org.apache.kafka.server.common.{ApiMessageAndVersion, KRaftVersion, MetadataVersion}
-import org.apache.kafka.server.config.{KRaftConfigs, ServerConfigs}
+import org.apache.kafka.server.config.{KRaftConfigs, ReplicationConfigs, ServerConfigs}
 import org.apache.kafka.server.log.remote.storage.RemoteLogManagerConfig
 import org.apache.kafka.server.quota
 import org.apache.kafka.server.quota.{ClientQuotaCallback, ClientQuotaType}
@@ -130,6 +130,32 @@ class KRaftClusterTest {
     }
   }
 
+  @Test
+  def testClusterWithLowerCaseListeners(): Unit = {
+    Using.resource(new KafkaClusterTestKit.Builder(
+      new TestKitNodes.Builder().
+        setNumBrokerNodes(1).
+        setBrokerListenerName(new ListenerName("external")).
+        setNumControllerNodes(3).
+        build()).build()
+    ) { cluster =>
+      cluster.format()
+      cluster.startup()
+      cluster.brokers().forEach((_, broker) => {
+        assertEquals("external://localhost:0", broker.config.get(SocketServerConfigs.LISTENERS_CONFIG))
+        assertEquals("external", broker.config.get(ReplicationConfigs.INTER_BROKER_LISTENER_NAME_CONFIG))
+        assertEquals("external:PLAINTEXT,CONTROLLER:PLAINTEXT", broker.config.get(SocketServerConfigs.LISTENER_SECURITY_PROTOCOL_MAP_CONFIG))
+      })
+      TestUtils.waitUntilTrue(() => cluster.brokers().get(0).brokerState == BrokerState.RUNNING,
+        "Broker never made it to RUNNING state.")
+      TestUtils.waitUntilTrue(() => cluster.raftManagers().get(0).client.leaderAndEpoch().leaderId.isPresent,
+        "RaftManager was not initialized.")
+      Using.resource(Admin.create(cluster.clientProperties())) { admin =>
+        assertEquals(cluster.nodes().clusterId(), admin.describeCluster().clusterId().get())
+      }
+    }
+  }
+
   @Test
   def testCreateClusterAndWaitForBrokerInRunningState(): Unit = {
     val cluster = new KafkaClusterTestKit.Builder(

core/src/test/scala/unit/kafka/server/KafkaConfigTest.scala

@@ -1869,4 +1869,12 @@ class KafkaConfigTest {
     props.put(ShareGroupConfig.SHARE_GROUP_RECORD_LOCK_DURATION_MS_CONFIG, "30000")
     assertDoesNotThrow(() => KafkaConfig.fromProps(props))
   }
+
+  @Test
+  def testLowercaseControllerListenerNames(): Unit = {
+    val props = createDefaultConfig()
+    props.setProperty(KRaftConfigs.CONTROLLER_LISTENER_NAMES_CONFIG, "controller")
+    val message = assertThrows(classOf[IllegalArgumentException], () => KafkaConfig.fromProps(props)).getMessage
+    assertEquals("requirement failed: controller.listener.names must contain at least one value appearing in the 'listeners' configuration when running the KRaft controller role", message)
+  }
 }

test-common/test-common-runtime/src/main/java/org/apache/kafka/common/test/KafkaClusterTestKit.java

@@ -556,7 +556,10 @@ public class KafkaClusterTestKit implements AutoCloseable {
             int brokerId = entry.getKey();
             BrokerServer broker = entry.getValue();
             ListenerName listenerName = nodes.brokerListenerName();
-            int port = broker.boundPort(listenerName);
+            // The KafkaConfig#listeners method normalizes the listener name.
+            // The result from TestKitNodes#brokerListenerName method should be normalized as well,
+            // so that it matches the listener name in the KafkaConfig.
+            int port = broker.boundPort(ListenerName.normalised(listenerName.value()));
             if (port <= 0) {
                 throw new RuntimeException("Broker " + brokerId + " does not yet " +
                     "have a bound port for " + listenerName + ".  Did you start " +
@@ -575,6 +578,9 @@ public class KafkaClusterTestKit implements AutoCloseable {
             int id = entry.getKey();
             ControllerServer controller = entry.getValue();
             ListenerName listenerName = nodes.controllerListenerName();
+            // Although the KafkaConfig#listeners method normalizes the listener name,
+            // the controller.listener.names configuration does not allow lowercase input,
+            // so there is no lowercase controller listener name, and we don't need to normalize it.
             int port = controller.socketServer().boundPort(listenerName);
             if (port <= 0) {
                 throw new RuntimeException("Controller " + id + " does not yet " +