Implement a tool or service like codesearch.debian.net, but for stable/oldstable/etc

Currently there is a service, https://codesearch.debian.net/, which can be used to search the code of all source packages in Debian. However, this indexes only the unstable distribution.

We should consider implementing a similar tool or service for searching code of stable, oldstable, and older distributions. Some notes are in order:

• this issue is really more of a placeholder, it is not intended to prompt any work in the short term
• considering the above, this has the potential to be a very large effort, so discussions of scope, design, and so on will certainly need to happen before anything is done
• it is possible that this issue should not even be in this project, but it is a placeholder and more suitable location is not immediately apparent
• a related project to look at is https://salsa.debian.org/debian/codesearch-cli (we probably want to think about the new service as a backend that could be selected by a switch to the CLI tool, similar to the --url option of rmadison)

With all of that, ideas or comments on this are more than welcome and can be recorded as comments in this issue.