jackson ObjectMapper: auto-detect modules (opensearch-project#1643)

jackson 2.x still supports java 7 and thus does not automatically
support java 8 classes. this will change with jackson 3.x (see e.g.
this [PR adding JSR310 date support] to 3.x).

PR opensearch-project#251 added documentation on how a custom `ObjectMapper` can be
registered - but there's no reason why we can't just enable
auto-detection centrally. the docs mention that performance should be
considered, but this is IMHO not relevant here since we only construct
it once and then keep the same `ObjectMapper` (which in turn the docs
mention as best practices).

Signed-off-by: Ralph Ursprung <Ralph.Ursprung@avaloq.com>

[PR adding JSR310 date support]: FasterXML/jackson-databind#5032

(cherry picked from commit c1ae512)
Signed-off-by: Thomas Farr <tsfarr@amazon.com>

Author: rursprung

CHANGELOG.md

@@ -3,6 +3,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 
 ## [Unreleased 2.x]
 ### Added
+- Added Jackson `ObjectMapper` module auto-detection ([#1643](https://github.com/opensearch-project/opensearch-java/pull/1643))
 
 ### Dependencies
 

USER_GUIDE.md

@@ -65,11 +65,12 @@ OpenSearchTransport transport = new RestClientTransport(restClient, new JacksonJ
 OpenSearchClient client = new OpenSearchClient(transport);
 ```
 
-The `JacksonJsonpMapper` class (2.x versions) only supports Java 7 objects by default. [Java 8 modules](https://github.com/FasterXML/jackson-modules-java8) to support JDK8 classes such as the Date and Time API (JSR-310), `Optional`, and more can be used by including [the additional datatype dependency](https://github.com/FasterXML/jackson-modules-java8#usage) and adding the module.  For example, to include JSR-310 classes:
+The `JacksonJsonpMapper` class (2.x versions) only supports Java 7 objects by default. [Java 8 modules](https://github.com/FasterXML/jackson-modules-java8) to support JDK8 classes such as the Date and Time API (JSR-310), `Optional`, and more can be used by including [the additional datatype dependency](https://github.com/FasterXML/jackson-modules-java8#usage) and adding the module. Auto-detection for these modules is enabled, adding them to the classpath is enough.
+You can also provide your own `ObjectMapper` instance if you need to pre-configure it differently, for example:
 
 ```java
-Transport transport = new RestClientTransport(restClient,
-    new JacksonJsonpMapper(new ObjectMapper().registerModule(new JavaTimeModule()))); 
+OpenSearchTransport transport = new RestClientTransport(restClient,
+    new JacksonJsonpMapper(new ObjectMapper().findAndRegisterModules().configure(SerializationFeature.INDENT_OUTPUT, true))); 
 OpenSearchClient client = new OpenSearchClient(transport);
 ```
 
@@ -194,4 +195,4 @@ You can find a working sample of the above code in [IndexingBasics.java](./sampl
 
 ## Plugins
 
-- [k-NN](guides/plugins/knn.md)
+- [k-NN](guides/plugins/knn.md)

java-client/src/main/java/org/opensearch/client/json/jackson/JacksonJsonpMapper.java

@@ -63,7 +63,9 @@ public JacksonJsonpMapper(ObjectMapper objectMapper, JsonFactory jsonFactory) {
 
     public JacksonJsonpMapper() {
         this(
-            new ObjectMapper().configure(SerializationFeature.INDENT_OUTPUT, false).setSerializationInclusion(JsonInclude.Include.NON_NULL)
+            new ObjectMapper().configure(SerializationFeature.INDENT_OUTPUT, false)
+                .setSerializationInclusion(JsonInclude.Include.NON_NULL)
+                .findAndRegisterModules()
         );
     }