chore: add a test with extracting a timestamp field from message metadata

Author: jerrinot

connector/src/test/java/io/questdb/kafka/QuestDBSinkConnectorEmbeddedTest.java

@@ -996,6 +996,46 @@ public void testDoNotIncludeKey(boolean useHttp) {
                 httpPort);
     }
 
+    @Test
+    public void testExtractKafkaIngestionTimestampAsField() {
+        connect.kafka().createTopic(topicName, 1);
+        Map<String, String> props = ConnectTestUtils.baseConnectorProps(questDBContainer, topicName, true);
+        props.put(QuestDBSinkConnectorConfig.DESIGNATED_TIMESTAMP_COLUMN_NAME_CONFIG, "birth"); // the field is injected via InsertField SMT
+        props.put(QuestDBSinkConnectorConfig.INCLUDE_KEY_CONFIG, "false");
+        props.put("transforms", "InsertField");
+        props.put("transforms.InsertField.type", "org.apache.kafka.connect.transforms.InsertField$Value");
+        props.put("transforms.InsertField.timestamp.field", "birth");
+        connect.configureConnector(ConnectTestUtils.CONNECTOR_NAME, props);
+        ConnectTestUtils.assertConnectorTaskRunningEventually(connect);
+
+        // note: there is no birth field in the message payload
+        Schema schema = SchemaBuilder.struct().name("com.example.Person")
+                .field("firstname", Schema.STRING_SCHEMA)
+                .field("lastname", Schema.STRING_SCHEMA)
+                .build();
+        Struct struct = new Struct(schema)
+                .put("firstname", "John")
+                .put("lastname", "Doe");
+
+        Map<String, Object> prodProps = new HashMap<>();
+        try (KafkaProducer<byte[], byte[]> producer = connect.kafka().createProducer(prodProps)) {
+            java.util.Date birth = new Calendar.Builder()
+                    .setTimeZone(TimeZone.getTimeZone("UTC"))
+                    .setDate(2022, 9, 23) // note: month is 0-based
+                    .setTimeOfDay(13, 53, 59, 123)
+                    .build().getTime();
+            long kafkaTimestamp = birth.getTime();
+            ProducerRecord<byte[], byte[]> producerRecord = new ProducerRecord<>(topicName, null, kafkaTimestamp, "key".getBytes(), new String(converter.fromConnectData(topicName, schema, struct)).getBytes());
+            producer.send(producerRecord);
+        }
+
+        QuestDBUtils.assertSqlEventually("\"firstname\",\"lastname\",\"timestamp\"\r\n"
+                        + "\"John\",\"Doe\",\"2022-10-23T13:53:59.123000Z\"\r\n",
+                "select * from " + topicName,
+                httpPort);
+    }
+
+
     @ParameterizedTest
     @ValueSource(booleans = {true, false})
     public void testJsonNoSchema(boolean useHttp) {