Java: Add release notes for release 5.16.0 (#2005)

* Add new release notes

* Update release-notes-15-to-29.mdx

---------

Co-authored-by: Jonas Israel <[email protected]>

Author: bot-sdk-js

docs-java/release-notes/release-notes-15-to-29.mdx

@@ -1,3 +1,21 @@
+## 5.16.0 - January 29, 2025
+
+[All Release Changes](https://github.com/SAP/cloud-sdk-java/releases/tag/rel%2F5.16.0)
+
+### ✨ New Functionality
+
+- Add experimental support for updating nested fields in OData v2 complex types via PATCH requests
+  - Use optional argument `FluentHelperUpdate#modifyingEntity( ModifyPatchStrategy )` to control updates with delta or full complex property payloads.
+
+### 📈 Improvements
+
+- Improve the OData v4 class `BatchRequestBuilder` to now also implement the `ModificationRequestBuilder` interface.
+
+### 🐛 Fixed Issues
+
+- Fix non-compilable code using OpenAPI generator with schema definitions having `additionalProperties: true`.
+  Previously they would result in model classes extending `HashMap`, which disabled proper deserialization and serialization.
+
 ## 5.15.0 - December 19, 2024
 
 [All Release Changes](https://github.com/SAP/cloud-sdk-java/releases/tag/rel%2F5.15.0)