Add Kafka sample

See gh-11597

spring-boot-samples/spring-boot-sample-kafka/src/main/java/sample/kafka/SampleMessage.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2012-2018 the original author or 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 sample.kafka;
+
+public class SampleMessage {
+	private Integer id;
+	private String message;
+
+	public Integer getId() {
+		return id;
+	}
+
+	public void setId(Integer id) {
+		this.id = id;
+	}
+
+	public String getMessage() {
+		return message;
+	}
+
+	public void setMessage(String message) {
+		this.message = message;
+	}
+
+	public SampleMessage() {
+	}
+
+	public SampleMessage(Integer id, String message) {
+		this.id = id;
+		this.message = message;
+	}
+
+	@Override
+	public String toString() {
+		return "SampleMessage{" +
+				"id=" + id +
+				", message='" + message + '\'' +
+				'}';
+	}
+}