add release note about changed signature (ros2#606)

* add release note about changed signature

Signed-off-by: William Woodall <[email protected]>

* fixup

Signed-off-by: William Woodall <[email protected]>

Author: wjwwood

source/Releases/Release-Foxy-Fitzroy.rst

@@ -104,6 +104,20 @@ For examples, see the `relevant changes to the demos. <https://github.com/ros2/d
 
 `Related pull request in launch_ros. <https://github.com/ros2/launch_ros/pull/122>`_
 
+rclcpp
+^^^^^^
+
+Change in Advanced Subscription Callback Signature
+""""""""""""""""""""""""""""""""""""""""""""""""""
+
+With the pull request [https://github.com/ros2/rclcpp/pull/1047](https://github.com/ros2/rclcpp/pull/1047) the signature of callbacks which receive the message info with the message has changed.
+Previously it used the ``rmw`` type ``rmw_message_info_t``, but now uses the ``rclcpp`` type ``rclcpp::MessageInfo``.
+The required changes are straightforward, and can be seen demonstrated in these pull requests:
+
+- [https://github.com/ros2/system_tests/pull/423/files](https://github.com/ros2/system_tests/pull/423/files)
+- [https://github.com/ros2/rosbag2/pull/375/files](https://github.com/ros2/rosbag2/pull/375/files)
+- [https://github.com/ros2/ros1_bridge/pull/253/files](https://github.com/ros2/ros1_bridge/pull/253/files)
+
 rclpy
 ^^^^^