How/Where are the ros2 doxygen API docs built?

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Hi!

I find myself looking at https://docs.ros2.org/foxy/api/rclcpp/ from time to time, and i often end up at the wrong version of this document, since the version string is hardcoded to "master" (https://github.com/ros2/rclcpp/blob/m...).

Changing this to the appropriate branch name seems reasonable, and since Doxygen supports environment variables this should not be too hard. I assume this is deployed during some CI step? Could anyone point me to where this is configured, such that i can submit a PR with this change?

I already stumbled upon https://github.com/ros2/ci, but this doesn't seem to be what i'm looking for... docs.ros2.org also seems to be deprecated? https://discourse.ros.org/t/docs-ros2...