[ros2] Port elevator to ROS2

[shiveshkhaitan]

Port gazebo_ros_elevator plugin to ROS2.

Example:

 <plugin name="elevator" filename="libgazebo_ros_elevator.so">
  <ros>
    <namespace>demo</namespace>
    <argument>elevator:=elevator_demo</argument>
  </ros>
  <bottom_floor>0</bottom_floor>
  <top_floor>1</top_floor>

  <lift_joint>elevator::lift</lift_joint>
  <door_joint>elevator::door</door_joint>
  <floor_height>3.075</floor_height>

  <!-- Time the elevator door will stay open in seconds -->
  <door_wait_time>10</door_wait_time>
</plugin>

Migration guide at ROS 2 Migration: Elevator

[chapulina]

Works for me!

I noticed that the elevator sometimes doesn't respond to commands. I needed to send a command a couple of times before it moved. But the problem seems to be in the Gazebo plugin, because I checked that the MoveToFloor commands are going through.

Merging!

[chapulina]

So strange that the original plugin takes a string when we need an int 🤔 We could easily change this to Int32 for a cleaner implementation.

I wonder if it was done like this because Gazebo's ElevatorPlugin uses a string message. And the reason for that is that gazebo::msgs doesn't have an integer message...