Add action_msgs::msg::GoalStatus::STATUS_PREEMPTED

[naiveHobo]

Signed-off-by: Sarthak Mittal sarthakmittal2608@gmail.com

As per ros2/rclcpp#1104 and the corresponding PR ros2/rclcpp#1117, this PR adds STATUS_PREEMPTED to action_msgs/GoalStatus to refer to a goal that was preempted by the client.

[jacobperron]

I don't think it's as simple as adding a new field to the message, there is also code in rcl_action and rclpy that works with GoalStatus. Before making further changes, I suggest a discussion and changes around the design of the state machine (see ros2/rclcpp#1104 (comment))

[fujitatomoya]

This fix itself is LGTM.

[SteveMacenski]

@jacobperron mentions that it may be worth adding the PREEMPTING as well - I agree as long as the intention is to add that to the state machine.

[SteveMacenski]

@naiveHobo I think the best route here is to add the PREEMPTING message he asked for so that these messages are complete and then work with Jacob to update the state machine. Given we had one like this for ROS1, it shouldn't be too big of an undertaking. Once we have the design and this message in place, we can get the rclcpp PR merged.