adding pluginized navigator (ros-navigation#380)

* adding pluginized navigator

* Update migration/Humble.rst

configuration/packages/configuring-bt-navigator.rst

@@ -16,6 +16,18 @@ Consider checking out the :ref:`groot_introduction` tutorial for using Groot to
 Parameters
 **********
 
+:navigators:
+
+  ============== ============================================================
+  Type           Default
+  -------------- ------------------------------------------------------------
+  vector<string> {'navigate_to_pose', 'navigate_through_poses'} 
+  ============== ============================================================
+
+  Description
+    New to Iron: Plugins for navigator types implementing the ``nav2_core::BehaviorTreeNavigator`` interface.
+    They implement custom action servers with custom interface definitions and use that data to populate and process behavior tree navigation requests. Plugin classes are defined under the same namespace, see examples below. Defaults correspond to the ``NavigateToPoseNavigator`` and ``NavigateThroughPosesNavigator`` navigators.
+
 :default_nav_to_pose_bt_xml:
 
   ====== =======
@@ -210,6 +222,11 @@ Example
         goal_blackboard_id: goal
         goals_blackboard_id: goals
         path_blackboard_id: path
+        navigators: ['navigate_to_pose', 'navigate_through_poses']
+        navigate_to_pose:
+          plugin: "nav2_bt_navigator/NavigateToPoseNavigator"
+        navigate_through_poses:
+          plugin: "nav2_bt_navigator/NavigateThroughPosesNavigator"
         plugin_lib_names: 
           - nav2_compute_path_to_pose_action_bt_node
           - nav2_follow_path_action_bt_node

migration/Humble.rst

@@ -5,6 +5,13 @@ Humble to Iron
 
 Moving from ROS 2 Humble to Iron, a number of stability improvements were added that we will not specifically address here.
 
+New Behavior-Tree Navigator Plugins
+***********************************
+
+New in `PR 3345 <https://github.com/ros-planning/navigation2/pull/3345>`_, the navigator types are exposed to users as plugins that can be replaced or new navigator types added. The default behaviors of navigate to pose and navigate through poses continue to be default behavior but are now customizable with new action interface definitions. These plugins implement the ``nav2_core::BehaviorTreeNavigator`` base class, which must process the action request, feedback, and completion messages. The behavior tree is handled by this base class with as much general logic as possible abstracted away from users to minimize repetition.
+
+See :ref:`writing_new_nav2navigator_plugin` for a tutorial about writing new navigator plugins.
+
 Added Collision Monitor
 ***********************
 `PR 2982 <https://github.com/ros-planning/navigation2/pull/2982>`_ adds new safety layer operating independently of Nav2 stack which ensures the robot to control the collisions with near obstacles, obtained from different sensors (LaserScan, PointCloud, IR, Sonars, etc...). See :ref:`configuring_collision_monitor` for more details. It is not included in the default bringup batteries included from ``nav2_bringup``.