kotlin-sdk-example

Based on https://antithesis.com/docs/using_antithesis/sdk/java/example/?sid=85141.0&sterm=java%20sdk

Used nix flake for maven, jdk, and kotlin

Use:

1. nix develop --extra-experimental-features flakes
2. mvn clean install
3. export ANTITHESIS_SDK_LOCAL_OUTPUT=assertions.json
4. mvn exec:java -Dexec.mainClass="AppKt"