docs: add changelog and upgrade

user_guide_src/source/changelogs/v4.5.0.rst

@@ -51,6 +51,13 @@ Due to a bug fix, the behavior has changed so that options passed to the outer
 ``group()`` are merged with the options of the inner ``group()``.
 See :ref:`Upgrading Guide <upgrade-450-nested-route-groups-and-options>` for details.
 
+API\\ResponseTrait
+------------------
+
+Now when a response format is JSON, if you pass string data, the framework returns
+a JSON response. In previous versions, it returned a HTML response.
+See :ref:`Upgrading Guide <upgrade-450-api-response-trait>` for details.
+
 Factories class
 ---------------
 

user_guide_src/source/installation/upgrade_450.rst

@@ -155,6 +155,20 @@ reversed.
         Previous: route1 → route2 → filter1 → filter2
              Now: route2 → route1 → filter2 → filter1
 
+.. _upgrade-450-api-response-trait:
+
+API\\ResponseTrait and String Data
+==================================
+
+In previous versions, if you pass string data to a trait method, the framework
+returned an HTML response, even if the response format was determined to be JSON.
+
+Now if you pass string data, it returns a JSON response correctly. See also
+:ref:`api-response-trait-handling-response-types`.
+
+You can keep the behavior in previous versions if you set the ``$stringAsHtml``
+property to ``true`` in your controller.
+
 FileLocator::findQualifiedNameFromPath()
 ========================================
 

user_guide_src/source/outgoing/api_responses.rst

@@ -24,6 +24,8 @@ exist for the most common use cases:
 
 .. literalinclude:: api_responses/002.php
 
+.. _api-response-trait-handling-response-types:
+
 ***********************
 Handling Response Types
 ***********************