Add test for KafkaEventRecord headers

Author: Peiyu Wu

aws-lambda-java-tests/src/test/java/com/amazonaws/services/lambda/runtime/tests/EventLoaderTest.java

@@ -82,6 +82,9 @@ public void testLoadKafkaEvent() {
 
         KafkaEvent.KafkaEventRecord record = event.getRecords().get("mytopic-01").get(0);
         assertThat(record.getValue()).decodedAsBase64().asString().isEqualTo("Hello from Kafka !!");
+         
+        String headerValue = new String(record.getHeaders().get(0).get("headerKey"));    
+        assertThat(headerValue).isEqualTo("headerValue");
     }
 
     @Test

aws-lambda-java-tests/src/test/resources/kafka_event.json

@@ -10,7 +10,24 @@
         "offset": 15,
         "timestamp": 1596480920837,
         "timestampType": "CREATE_TIME",
-        "value": "SGVsbG8gZnJvbSBLYWZrYSAhIQ=="
+        "value": "SGVsbG8gZnJvbSBLYWZrYSAhIQ==",
+        "headers": [
+          {
+            "headerKey": [
+              104,
+              101,
+              97,
+              100,
+              101,
+              114,
+              86,
+              97,
+              108,
+              117,
+              101
+            ]
+          }
+        ]
       }
     ]
   }