Document JDK version support philosohpy

Author: emlun

doc/development.md

@@ -2,6 +2,27 @@ Developer docs
 ===
 
 
+JDK versions
+---
+
+The project's official build JDK version is the latest LTS JDK version,
+although the project may lag behind the true latest release for a while
+until we can upgrade the build definition to match this target.
+
+The official build JDK version currently in effect is encoded in the
+["Reproducible binary"](https://github.com/Yubico/java-webauthn-server/blob/main/.github/workflows/release-verify-signatures.yml)
+workflow,
+as the JDK version is crucial for successfully reproducing released binaries.
+This version is also enforced in the release process in
+[`build.gradle`](https://github.com/Yubico/java-webauthn-server/blob/main/build.gradle).
+
+The [primary build workflow](https://github.com/Yubico/java-webauthn-server/blob/main/.github/workflows/build.yml)
+should run on all currently maintaned LTS JDK versions,
+and ideally also the latest non-LTS JDK version if Gradle and other build dependencies are compatible.
+
+A list of JDK versions and maintenance status can be found [here](https://en.wikipedia.org/wiki/Java_version_history).
+
+
 Setup for publishing
 ---