DOCSP-20939: what's new updates for 4.5 (#208)

* DOCSP-20939: what's new updates for 4.5

Author: Chris Cho

source/whats-new.txt

@@ -12,12 +12,38 @@ What's New
 
 Learn what's new in:
 
+* :ref:`Version 4.5 <version-4.5>`
 * :ref:`Version 4.4 <version-4.4>`
 * :ref:`Version 4.3 <version-4.3>`
 * :ref:`Version 4.2 <version-4.2>`
 * :ref:`Version 4.1 <version-4.1>`
 * :ref:`Version 4.0 <version-4.0>`
 
+.. _version-4.5:
+
+What's New in 4.5
+-----------------
+
+New features of the 4.5 Java driver release include:
+
+- Added support for specifying custom service names of SRV resource
+  records. See the ``srvServiceName`` setting in the :ref:`Connection
+  Options <connection-options>` guide for more information.
+- Added support to customize UUID representation in a codec registry using
+  the ``CodecRegistries.withUuidRepresentation()`` method.
+- Added support for overriding listener settings in ``ClusterSettings``,
+  ``ServerSettings`` and ``ConnectionPoolSettings`` builders. 
+- All events received by ``ClusterListener``, ``ServerListener``, and
+  ``ServerMonitorListener`` are now totally ordered using
+  a happens-before relationship when the listeners are not shared by
+  different MongoClient instances. To learn more about the happens-before
+  ordering, see `Happens-before Order <https://docs.oracle.com/javase/specs/jls/se17/html/jls-17.html#jls-17.4.5>`__
+  in the Java Language Specification.
+- Added ``EnumCodec`` and ``EnumCodecProvider`` classes to separate codec 
+  support for enum types from the ``PojoCodec`` class.
+- Resolved performance issues that impacted versions 4.4 and 4.3 of the
+  driver. Performance in this version should be similar to performance in 4.2.
+
 .. _version-4.4:
 
 What's New in 4.4