docker-entrypoint.sh has no automated test, so entrypoint changes ship unverified by CI #13

docker-entrypoint.sh translates three environment variables into JVM system properties (BACKUP_DIRECTORY, SCHEDULED_USERS, and BACKUP_INTERVAL_MS as of PR #12), but no test exercises it.

Neither CI job covers the script:

• build runs mvn clean verify, which cannot execute a shell script.
• docker-build builds the image, which confirms the script is copied and made executable, but never starts a container, so the branches inside the script are never run.

The result is that any change to the entrypoint — including the one merged in PR #12 — lands with a fully green CI run while the changed lines have never been executed. A typo in a property name or a broken guard would not be caught until a user's container came up with the wrong configuration.

Suggested resolution:

• A test script is added that puts a stub java on PATH (one that prints its argv rather than starting a JVM), invokes docker-entrypoint.sh under a few environment combinations, and asserts the constructed argument list. Cases worth covering: no variables set, each variable set individually, all three set together, and a variable set to the empty string (which must not append an argument).
• A step is added to the docker-build job in .github/workflows/build.yml to run that script. GitHub Actions' ubuntu-latest runner can execute sh directly, so no container is required.

Optionally, shellcheck is run over docker-entrypoint.sh in the same step to catch quoting and portability problems.

This gap was identified during the self-review of PR #12 (#12), where the entrypoint change could not be executed and had to be accepted on hand review alone.

This issue was filed during a Gardener session (https://github.com/Stephenson-Software/gardener).

drafted by Claude on behalf of Daniel Stephenson