introduce sonarqube and test infrastructure (as in dmx-sign-up-ui)

Needs a project in sonarqube including a project key.

Starting point: https://sonar.dmx.systems/projects/create?mode=gitlab As in dmx-sign-up-ui:

-Dsonar.projectKey=dmx-plugins_dmx-sign-up-ui_AYxEI3BYvTOXKGTcYQio
``