feat: Update README.md and add tests

README.md

@@ -256,6 +256,7 @@ under [the specified folder](examples/with-sasl-plaintext) and then start the ap
 | `retryConfiguration.sasl.password`               | SCRAM OR PLAIN password                                                                                                                                                                                                                                                                                                                                                                                 |                             |
 | `retryConfiguration.skipMessageByHeaderFn`       | Function to filter messages based on headers, return true if you want to skip the message	                                                                                                                                                                                                                                                                                                              | nil                         |
 | `batchConfiguration.messageGroupLimit`           | Maximum number of messages in a batch                                                                                                                                                                                                                                                                                                                                                                   |                             |
+| `batchConfiguration.messageGroupByteSizeLimit`   | Maximum number of bytes in a batch                                                                                                                                                                                                                                                                                                                                                                      |                             |
 | `batchConfiguration.batchConsumeFn`              | Kafka batch consumer function, if retry enabled it, is also used to consume retriable messages                                                                                                                                                                                                                                                                                                          |                             |
 | `batchConfiguration.preBatchFn`                  | This function enable for transforming messages before batch consuming starts                                                                                                                                                                                                                                                                                                                            |                             |
 | `batchConfiguration.balancer`                    | [see doc](https://pkg.go.dev/github.com/segmentio/kafka-go#Balancer)                                                                                                                                                                                                                                                                                                                                    | leastBytes                  |

message_test.go

@@ -98,6 +98,25 @@ func TestMessage_AddHeader(t *testing.T) {
 	})
 }
 
+func TestMessage_Size(t *testing.T) {
+	// Given
+	m := Message{
+		Headers: []kafka.Header{
+			{Key: "foo", Value: []byte("fooValue")},
+		},
+		Value: []byte("barValue"),
+		Key:   []byte("bar"),
+	}
+
+	// When
+	s := m.TotalSize()
+
+	// Then
+	if s != 46 {
+		t.Fatalf("Total message size must be equal to 46")
+	}
+}
+
 func TestMessage_RemoveHeader(t *testing.T) {
 	// Given
 	m := Message{