Setup Scala

Combining setup-java & setup-sbt with good defaults for the Guardian

Java version

• Java distribution used: always the AWS Corretto distribution of Java, the standard Java distro used at the Guardian.

Note that (like gha-scala-library-release-workflow) guardian/setup-scala requires that projects specify their Java version with an asdf-formatted .tool-versions file.

Only Java major version is respected

Although asdf requires a fully-specified Java version (eg 21.0.3.9.1) in the .tool-versions file, currently the workflow will only match the major version of Java specified in the file (eg 21).

This is due to limitations in actions/setup-java.