Support Java 17

[ljdelight]

At the moment the project is compiled using java 11 and many dependencies may not work on Java 17. The play framework docs say they're pushing to drop Java 11 soon, so it would be good to move away from Java 11.

The GH Actions can run for both Java 11 and Java 17

Play 2.9 dropped Java 8 support and requires at least Java 11. Other supported Java versions are 17 and 21. When upgrading to Play 2.9, we strongly recommend considering an upgrade to at least Java 17 LTS. It’s worth noting that in the forthcoming Play 2.x release, which will be version 2.10, we are likely to discontinue support for Java 11.