docs: add changelog and upgrade guide

Author: kenjis

user_guide_src/source/changelogs/v4.3.0.rst

@@ -320,6 +320,7 @@ Others
 - **View:** Added ``Controlled Cells`` that provide more structure and flexibility to your View Cells. See :ref:`View Cells <controlled-cells>` for details.
 - **Validation:** Added Closure validation rule. See :ref:`validation-using-closure-rule` for details.
 - **Config:** Now you can specify Composer packages to auto-discover manually. See :ref:`Code Modules <modules-specify-composer-packages>`.
+- **Config:** Added ``Config\Session`` class to handle session configuration.
 - **Debug:** Kint has been updated to 5.0.1.
 - **Request:** Added new ``$request->getRawInputVar()`` method to return a specified variable from raw stream. See :ref:`Retrieving Raw data <incomingrequest-retrieving-raw-data>`.
 
@@ -353,6 +354,7 @@ Deprecations
 - The public property ``IncomingRequest::$uri`` is deprecated. It will be protected. Use ``IncomingRequest::getUri()`` instead.
 - The public property ``IncomingRequest::$config`` is deprecated. It will be protected.
 - The method ``CLI::isWindows()`` is deprecated. Use ``is_windows()`` instead.
+- The ``Config\App`` session properties in favor of the new session config class ``Config\Session``.
 
 Bugs Fixed
 **********

user_guide_src/source/installation/upgrade_430.rst

@@ -272,6 +272,8 @@ Config
 - app/Config/Security.php
     - Changed the value of the property ``$redirect`` to ``false`` to prevent redirection when a CSRF
       check fails. This is to make it easier to recognize that it is a CSRF error.
+- app/Config/Session.php
+    - Added to handle session configuration.
 - app/Config/Validation.php
     - The default Validation Rules have been changed to Strict Rules for better security. See :ref:`validation-traditional-and-strict-rules`.