DOCSP-25464: RecordCodec changes in v4.8 (#300)

* DOCSP-25464: RecordCodec changes in v4.8

Author: Chris Cho

source/upgrade.txt

@@ -64,6 +64,22 @@ Version 4.8 Breaking Changes
   module if your application deploys the driver in an OSGi container and
   relies on the driver for encoding and decoding Java records.
 
+- The ``RecordCodec``, implemented in v4.6, deserialized POJOs and record
+  classes that are specified as type parameters of ``List`` or ``Map`` fields
+  of a record as ``Document`` values instead of their respective classes. This
+  version now deserializes them to the proper record and POJO types.
+
+  For example, the following record class definitions show a ``Book`` record
+  that contains a ``List`` that receives a ``Chapter`` type parameter:
+
+  .. code-block:: java
+
+     public record Book(String title, List<Chapter> chapters) {}
+     public record Chapter(Integer number, String text) {}
+
+  Starting in this version, the codec deserializes data in the ``List`` into
+  ``Chapter`` record classes instead of ``Document`` values.
+
 .. _java-breaking-changes-v4.7:
 
 Version 4.7 Breaking Changes
@@ -157,7 +173,7 @@ Version 4.8 Server Release Support Changes
 
 - The v4.8 driver drops support for {+mdb-server+} v3.4 and earlier.
   To use the v4.8 driver, your {+mdb-server+} must be v3.6 or later. To learn
-  how to upgrade your {+mdb-server+} to v3.6, follow the link that corresponds 
+  how to upgrade your {+mdb-server+} to v3.6, follow the link that corresponds
   to your MongoDB deployment configuration:
 
   - :ref:`<3.6-upgrade-replica-set>`

source/whats-new.txt

@@ -31,9 +31,15 @@ Learn what's new in:
 What's New in 4.8
 -------------------
 
-The 4.8 driver ends support for MongoDB v3.4 and earlier. To learn
-more about breaking changes in this driver version and how to address 
-them, see :ref:`<java-server-release-change-v4.8>`.
+- The 4.8 driver ends support for MongoDB v3.4 and earlier. To learn
+  more about breaking changes in this driver version and how to address
+  them, see :ref:`<java-server-release-change-v4.8>`.
+
+- The ``RecordCodec`` now deserializes POJOs and record classes that are
+  specified as type parameters of ``List`` and ``Map`` fields of a record as
+  their respective classes. To learn more about this change and how this may 
+  affect the behavior of your application, see
+  :ref:`<java-breaking-changes-v4.8>`.
 
 Behavioral changes with the 4.8 driver release include: