Feature request

Feature description

At the moment the getLookAheadPoint() function takes the last point on the path if the look ahead distance would put it past the last point. This has the effect of increasing the gain of the steering inputs (ie the look ahead distance is reduced).
https://github.com/ros-planning/navigation2/blob/210977790bfb6e809f2c2ef3b7e1660662d630cc/nav2_regulated_pure_pursuit_controller/src/regulated_pure_pursuit_controller.cpp#L323-L325

We are using an Ackermann steered vehicle and having the carrot be so close to the robot makes for very unstable motion. When the robot pose is close to the final point in the path small deviations create large steering efforts, and inevitably full-lock steering just before the path is completed.

Implementation considerations

Project carrot off the end of the last path segment in RPP controller. There is various collision checking, etc that is based on the carrot position, so this "augmented carrot" would have to be implemented such that those functions are unchanged.

If this sounds like the thing to do, I'll get on to writing something.