GH-3343: Fluent API for CharacterStreamWritingMH

Resolves #3343

Author: garyrussell

spring-integration-stream/src/main/java/org/springframework/integration/stream/CharacterStreamWritingMessageHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -124,6 +124,17 @@ public void setShouldAppendNewLine(boolean shouldAppendNewLine) {
 		this.shouldAppendNewLine = shouldAppendNewLine;
 	}
 
+	/**
+	 * Fluent api for {@link #setShouldAppendNewLine(boolean)}.
+	 * @param append true to append a newline.
+	 * @return this.
+	 * @since 5.4
+	 */
+	public CharacterStreamWritingMessageHandler appendNewLine(boolean append) {
+		setShouldAppendNewLine(append);
+		return this;
+	}
+
 	@Override
 	public String getComponentType() {
 		return "stream:outbound-channel-adapter(character)";