Add getter for ObjectMapper to JacksonMapper

Author: olegz

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/json/JacksonMapper.java

@@ -46,6 +46,10 @@ public void configureObjectMapper(Consumer<ObjectMapper> configurer) {
 		configurer.accept(mapper);
 	}
 
+	public ObjectMapper getObjectMapper() {
+		return this.mapper;
+	}
+
 	@Override
 	protected <T> T doFromJson(Object json, Type type) {
 		T convertedValue = null;