Set up a tool that produces code quality metrics and reports code smells

[CSchoel]

• Register the project in a code quality tool like SonarQube or LGTM
  • Suggested sources for help: help page of LGTM, the SCM team (in order to obtain rights to create a SonarQube project)
• Configure SonarQube/LGTM so that it shows as much meaningful information as possible
• If necessary, ensure that the code quality is checked for every commit to the main branch
• Add a badge for the overall code quality of the project to the README

[CSchoel]

I have set up a SonarQube project fort this: https://scm.thm.de/sonar/dashboard?id=MopeSWTP-SS21

However, I still need to fix the errors in feature/sonarQube in order to incorporate the code quality check into our CI pipeline.

[CSchoel]

I created another pull request that also enables code coverage via SonarQube. I also went through all SonarQube settings and tried to increase the amount of checks that were being done, but apparently there is only very coarse support for selecting which things should be checked.