refactor: replace JUnit assertion in ScramInitialiser

[lntutor]

Type of change

• Refactoring

Description

Replaces the JUnit assertTrue call in ScramInitialiser production code with an explicit Java state check and a descriptive IllegalStateException.

Additional Context

This removes the production dependency on JUnit assertions while preserving Awaitility's retry behavior until every configured SCRAM user is visible.

Fixes #667

Checklist

• Write tests
• Make sure all tests pass
• Update documentation (not needed)
• Reference relevant issue(s) and close them after merging
• Update CHANGELOG.md (not needed)

Verification

• mvn -pl impl -am -Dtest=ScramInitialiserTest -Dsurefire.failIfNoSpecifiedTests=false process-sources test on Java 21

[lntutor]

Current head 16e9e646ae66485b2a8b9a51adb2744d46b28638 is mergeable, the visible DCO check is green on that exact SHA, and there are no review threads or review-body comments open on the PR at the moment. If this assertion cleanup still matches the intended direction, it looks ready for maintainer review/merge when convenient.

[robobario]

Thanks @lntutor! The implementation looks good to me, but I'd rather merge with no unit test than the bytecode string comparison.

[robobario]

LGTM

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
50.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud