[luisfelipewb]

competition.launch.py has two ways to spawn: config_file:= sets the pose (and supports several vehicles) but ignores any URDF, while urdf:= sets the URDF but uses the fixed default pose. So a custom vehicle can't be spawned at a chosen position.

This PR lets each spawn config entry set urdf, and set_urdf() resolves package://<pkg>/<path> against the package's share directory, so both the config key and the existing urdf:= argument accept it:

- model_name: my_boat
  model_type: usv
  urdf: package://my_boat_gazebo/urdf/my_boat.urdf.xacro
  position:
    xyz: [-532, 162, 0.1]
    rpy: [0, 0, 1]

Entries without urdf behave as before. Related: #894 (robot_state_publisher uses the model name, needed for vehicles not named wamv).

Testing

Ubuntu 24.04, ROS 2 Jazzy, Gazebo Harmonic:

• urdf:=package://wamv_gazebo/urdf/wamv_gazebo.urdf.xacro resolves to the installed path and the WAM-V spawns as before.
• Together with Use the model name for robot_state_publisher #894, the Kingfisher ASV spawns from its own xacro at the configured pose, using this spawn config in sydney_regatta and a custom world: