Dces 670 tests refactoring

[vvartakMoJ]

What

Link to story

1. Use ValidationException instead of ResponseStatusException for consistency with other code.
2. Use AssertJ fluent assertions
3. Use given-when-then style names for test methods

Checklist

Before you ask people to review this PR:

• Tests should be passing: ./gradlew test
• Github should not be reporting conflicts; you should have recently run git rebase main.
• Avoid mixing whitespace changes with code changes in the same commit. These make diffs harder to read and conflicts more likely.
• You should have looked at the diff against main and ensured that nothing unexpected is included in your changes.
• You should have checked that the commit messages say why the change was made.

Additional checks

• Don’t forget to run the MAAT functional test suite after deploying your changes to the DEV or TEST environments to ensure your changes haven’t broken any of the functional tests.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud

[dconneely]

Obviously needs MAAT API team to approve as well, but looks pretty comprehensive to me

[karlbaker02]

👍