[Spike] Try out SonarQube

[binkley]

This is part of the #462 epic on plugins for quality.
Confirm if there are non-commercial ways to use, if so document, else only link.

Try out SonarQube and see what you think. When evaluating refer to the questions in the epic and upon completion add your pros and cons for this plugin as a comment to the aforementioned story.

This would not be a plugin to the local build, but something running in CI. It's the engine that powers IntelliJ inspections. There's probably a way to run it locally.

Refs

• https://github.com/marketplace/actions/official-sonarqube-scan
• https://docs.sonarsource.com/sonarqube/latest/analyzing-source-code/scanners/sonarscanner-for-gradle/
• https://docs.sonarsource.com/sonarqube/latest/analyzing-source-code/scanners/sonarscanner-for-maven/