Improvement Idea: Mark Packages as Deprecated

[danthony06]

I would like a way to tell bloom that certain packages, or even messages or nodes, are deprecated and will be removed at a later date. When a user installs the corresponding package, they would get a message through apt (or dnf, etc.) with that warning.

This came up when we were internally brainstorming how to solve issues related to this problem: swri-robotics/gps_umd#63. We've got pure message packages that we would like to deprecate, but to our knowledge, there's no good way of communicating this to the users. Most people do not build this from source, so we can't put a build warning in the package. I suspect most of our users don't see the Discourse site, so making an announcement there would have limited effect. This came up as a way of communicating our intention to anyone using this package.

Edit: I think this is the mechanism we might use, but i'm not very familiar with making debians: https://www.debian.org/doc/debian-policy/ch-binary.html#prompting-in-maintainer-scripts.