What is the status of rdmanifests?

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The pylon_camera package installation procedure instructs users to add a custom source to their local rosdep (15-pylon_camera.list) containing two source::uri elements that point to a single rdmanifest file: pylon_sdk.rdmanifest. That rdmanifest then is used to make rosdep satisfy the libpylon(-dev) dependency (when used with rosdep install ..).

I can still remember the time when the main rosdep database included snippets of bash (or even things coming close to full scripts), package-local yaml files with similar lines and rdmanifest files being distributed with packages. I also remember a major cleanup of rosdep to remove all that (because of running arbitrary snippets of shell script with super-user permissions, rosdep silently changing a system's configuration (by adding ppas or other apt repositories fi), and because it was just generally not maintainable nor scalable).

Seeing a recently created package like pylon_camera use something like rdmanifests makes me wonder what the official status is of those particular pieces of the rosdep infrastructure, and whether current users / packagers / maintainers should be discouraged from relying on them?

Afaik the buildfarm will also not build packages that rely on this (deprecated?) functionality, so perhaps that is deterrent enough already, but an authoritative answer would be nice to have.