I work on an extension for Postgres. We originally developed the extension for Postgres 11. Now we are looking into supporting newer versions of Postgres. We would like our extension to be compatible with multiple versions of Postgres. Is there a document that explains how the Postgres community handles releases and supports older versions? Any information on how Postgres handles this will give us guidance on how to best approach this subject.
This really isn't the right place to ask this kind of question. -general would be a good place, you'll still reach the people who can respond intelligently. I'll toss out my $0.02 here though I'm not that deep in the weeds on the topic.
Major releases don't really make any promises but we do try not to break things that worked in older versions gratuitously. Usually you need your code to perform version detection and adapt its behavior accordingly. But since the library code needs to be compiled for a particular version there is some room customization there if desired. You will want your extension to directly support at least two major version simultaneously so people can upgrade the extension alongside the PostgreSQL version upgrade without having to change their code on-the-fly.