enhance test and add todo

Author: christophstrobl

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/MongoCustomConversions.java

@@ -312,6 +312,7 @@ public MongoConverterConfigurationAdapter useSpringDataJavaTimeCodecs() {
 			return useNativeDriverJavaTimeCodecs(false);
 		}
 
+		// TODO: might just be a flag like the time codec?
 		public MongoConverterConfigurationAdapter numericFormat(String format) {
 			this.numericFormat = format;
 			return this;

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/convert/MappingMongoConverterUnitTests.java

@@ -3395,14 +3395,13 @@ void usesConfiguredNumericFormat() {
 
 		BigDecimalContainer container = new BigDecimalContainer();
 		container.value = BigDecimal.valueOf(2.5d);
-//		container.map = Collections.singletonMap("foo", container.value);
+		container.map = Collections.singletonMap("foo", container.value);
 
 		org.bson.Document document = new org.bson.Document();
 		converter.write(container, document);
 
 		assertThat(document.get("value")).isInstanceOf(Decimal128.class);
-//		assertThat((String) document.get("value")).isEqualTo("2.5");
-//		assertThat(((org.bson.Document) document.get("map")).get("foo")).isInstanceOf(String.class);
+		assertThat(((org.bson.Document) document.get("map")).get("foo")).isInstanceOf(Decimal128.class);
 	}
 
 	org.bson.Document write(Object source) {