Update doc to clarify BEST_EFFORT behavior when switching controllers (#2448) (#2450)

Author: mergify[bot]

controller_manager_msgs/srv/SwitchController.srv

@@ -5,11 +5,16 @@
 # To switch controllers, specify
 #  * the list of controller names to activate,
 #  * the list of controller names to deactivate, and
-#  * the strictness (BEST_EFFORT or STRICT)
+#  * the strictness (STRICT, BEST_EFFORT, AUTO, or FORCE_AUTO)
 #    * STRICT means that switching will fail if anything goes wrong (an invalid
-#      controller name, a controller that failed to activate, etc. )
-#    * BEST_EFFORT means that even when something goes wrong with one controller,
-#      the service will still try to activate/deactivate the remaining controllers
+#      controller name, a controller that failed to activate, etc.).
+#    * BEST_EFFORT:
+#      Transitions are only triggered if the controller is not yet in the target state.
+#      If it is already in the target state, no error occurs.
+#      Returns 'false' if all controllers of 'activate_controllers' or 'deactivate_controllers' are not yet loaded or configured,
+#      or the pending transitions of all existing controllers of 'activate_controllers'
+#      or 'deactivate_controllers' fail.
+#      Returns 'true' otherwise.
 #    * AUTO means that the controller manager will automatically resolve the controller
 #      chain in order to activate and/or deactivate the specified controllers.
 #      This is useful in complex systems when you want all dependent controllers to start
@@ -28,9 +33,9 @@
 #  * the timeout before aborting pending controllers. Zero for infinite
 
 # The return value "ok" indicates if the controllers were switched
-# successfully or not.  The meaning of success depends on the
+# successfully or not. The meaning of success depends on the
 # specified strictness.
-# The return value "message" provides some human-readable information
+# The return value "message" provides some human-readable information.
 
 
 string[] activate_controllers