Add unit tests

[slominskir-coding-agent]

The project had no tests. This adds JUnit 6 (org.junit:junit-bom:6.1.3) and 32 tests for the code that decides what runs on deploy hosts. CI's ./gradlew build (jeffersonlab/java-workflows unit-ci.yaml) runs them.

Tests

• DeployerFacadeTest (23): who may deploy (the env's request service user and adm-admin can; another user, an empty name, and anonymous can't), an unknown app env, and the semver check. The version is appended to a command run in a shell, so the rejected versions include 1.0.0; rm -rf /, 1.0.0|id, 1.0.0-$(id), a trailing newline, and a trailing space. Collaborators are small subclass fakes, plus a Proxy for SessionContext, so no mocking library is needed.
• SSHFacadeTest (5): runs asyncExecuteRemoteCommand against an in-process MINA SSH server whose commands are scripted in Java, so there's no shell or container to set up. It checks that the version is appended, a nonzero exit keeps its exit code and output (Record the deploy command's real exit code and output #17), a prompt gets no input (Give deploy commands empty input #20), a hanging command times out (Time out deploy commands after 10 minutes #19), and a failed login is recorded. The client uses a generated key and ignores ~/.ssh (keys, config, known_hosts), so running the tests never touches the developer's SSH files.
• FunctionsTest (4): the duration text on /log.

Changes to production code

SSHFacade gets two package-private seams for its test:

• createClient() returns SshClient.setUpDefaultClient(), as before; the test overrides it.
• commandTimeout is no longer final, so the test can shorten it.

The README's Develop section says how to run the tests.

Checks

• ./gradlew spotlessCheck build passes in the gradle:9-jdk21 container; the tests take about 3 seconds.
• Each test catches what it's for: with the code broken on purpose (no empty stdin, no version appended, no authorization check), promptGetsNoInput, versionIsAppendedToCommand, and otherUserCannotDeploy failed.

Found while writing the tests

A deploy request without a ver parameter throws a NullPointerException from Pattern.matcher(null) in DeployerFacade.validateSemver, rather than the "Version string must be semver formatted" message. I left it out of this PR, so there's no test for a null version.

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[slominskir]

Certainly better than no tests...