Rudder

UPDATE: as of JDK15, nashorn is removed.

GraalJS seems the best solution:
- it can run on openjdk as a simple lib dep: https://github.com/graalvm/graaljs/blob/master/docs/user/RunOnJDK.md
- it has nashorn compatible mode: https://github.com/graalvm/graaljs/blob/master/docs/user/ScriptEngine.md

Security will need to be updated.

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Since OpenJDK 11, we get a warning: "Warning: Nashorn engine is planned to be removed from a future JDK release".

The fact that nashorn will be removed is terrible, and we will need to address that. Some reference links seems to tell that we will need to switch to GraalVM at some point:

junit-team/junit5#1481
https://openjdk.java.net/jeps/335
https://jaxenter.com/nashorn-javascript-engine-deprecated-145320.html
https://www.infoworld.com/article/3291322/javascript/oracle-switch-now-from-nashorn-javascript-engine-to-graalvm.html
https://medium.com/graalvm/oracle-graalvm-announces-support-for-nashorn-migration-c04810d75c1f

In the meantime, we get a bad, red error message at startup, and we should really hide it, because rudder user really don't care about that. We need to add at startup options:

-Dnashorn.args="--no-deprecation-warning"