WIP: RAT-293: Add properties for SonarCloud integration

[ottlinger]

Allow RAT to integrate with Sonarcloud.io-scanning services.

https://issues.apache.org/jira/browse/RAT-293

[ottlinger]

Problems with animal-sniffer/jdk8-compliance:

[ERROR] Failed to execute goal org.sonarsource.scanner.maven:sonar-maven-plugin:3.9.1.2184:sonar (default-cli) on project apache-rat-project: Execution default-cli of goal org.sonarsource.scanner.maven:sonar-maven-plugin:3.9.1.2184:sonar failed: An API incompatibility was encountered while executing org.sonarsource.scanner.maven:sonar-maven-plugin:3.9.1.2184:sonar: java.lang.UnsupportedClassVersionError: org/sonar/batch/bootstrapper/EnvironmentInformation has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
[ERROR] -----------------------------------------------------
[ERROR] realm =    plugin>org.sonarsource.scanner.maven:sonar-maven-plugin:3.9.1.2184
[ERROR] strategy = org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy

[ottlinger]

Looks simple. Is there any reason not to merge this?

This cannot be merged as long as Sonar's plugin is not compiled with Java8 as it breaks our "JDK-8-only animal sniffer check" OR we decide to drop our hard-JDK8-compliance.

[Claudenw]

We could compile under multiple JDKs 8 and 20 for example. We should be dropping 8 in the next couple of years.

[Claudenw]

Now that we are testing under multiple JVM versions it should be possible to add the SonarCloud under a profile that runs when the JVM is not Java8. At least I think this is possible.