Drop Debian Stretch as it's EOL

[BryanQuigley]

It EOLs on June 30, 2022 per https://wiki.debian.org/LTS/Stretch.

[tianon]

Thanks for getting this started! ❤️

I think we need to do two things here:

1. wait for something like https://lists.debian.org/debian-announce/2020/msg00003.html to make the EOL "official" 😇

2. make sure we don't update the "default" for these two versions (for the same reason we still support stretch on them to begin with: Debian Buster is going to cause some reindexing headaches #582); I believe this means keeping debianSuites and setting both values to the empty string:

   postgres/versions.sh

   Line 79 in 2f6878c

   versionDebianSuite="${debianSuites[$version]-$defaultDebianSuite}" # intentionally missing ":" so it can be empty (again, https://github.com/docker-library/postgres/issues/582 😭)

I'm happy to take over and look at making the changes for 2. there if you want. 👍

[BryanQuigley]

Thanks for the quick review!

1. Not sure need to wait for the official announcement unless there is a chance it will be extended?
2. I believe I made the necessary changes for this- it's set to nothing for postgres 10 and 11.

[tianon]

I'd like to keep it until the official announcement because we might get one more supported base image rebuild before it's officially EOL 😅

[tianon]

Looks good -- I verified that generate-stackbrew-library.sh generates the appropriate thing (same as what exists right now, but minus the two stretch entries).

Now we just need the EOL to be official 👍

[tianon]

https://lists.debian.org/debian-lts-announce/2022/07/msg00002.html 🎉 ❤️