yoj-json-jackson-v2: Make `JacksonJsonConverter.createDefaultObjectMa…

…pper()`` public

...to potentially share YOJ's recommended `ObjectMapper` with other code in users' applications

json-jackson-v2/src/main/java/tech/ydb/yoj/repository/db/json/JacksonJsonConverter.java

@@ -109,7 +109,10 @@ public String toString() {
         return "JacksonJsonConverter";
     }
 
-    private static ObjectMapper createDefaultObjectMapper() {
+    /**
+     * @return {@code ObjectMapper} with reasonable defaults for mapping between Java objects and JSON
+     */
+    public static ObjectMapper createDefaultObjectMapper() {
         ObjectMapper mapper = new ObjectMapper();
         mapper.setTimeZone(TimeZone.getDefault());
         mapper.registerModule(new Jdk8Module());