Configuration of Github vars and secret to enable Sonarcloud scanning

Hi Eclipse,

Project: iot.kapua

We need the configuration of the following envs/secrets on out GitHub repo to enable Sonarcloud reporting on PRs and branches.

type	name	value
secrets	GITHUB_TOKEN
secrets	SONAR_TOKEN
vars	SONAR_ORGANIZATION_KEY	eclipse
vars	SONAR_PROJECT_KEY	org.eclipse_kapua

In this PR we added the GitHub Action to trigger the scan: https://github.com/eclipse/kapua/pull/3793 Following the guide from Sonarcloud: https://sonarcloud.io/project/configuration/GitHubActions?id=org.eclipse_kapua

Thanks