Integration of M-Elo

[Nimeggis]

Checklist for reviewer

• The code works and does not throw errors
• The code is easy to understand and there are no confusing parts
• The code follows the coding guidelines of this project
• The code change accomplishes what it is supposed to do
• I cannot think of any use case in which the code does not behave as intended
• The added and existing tests reasonably cover the code change
• I cannot think of any test cases, input or edge cases that should be tested in addition
• Description of the change is included in the documentation

[PaulBredl]

In dem PR sind einige SonarQube Issues. Die sind glaube ich alle nicht schlimm, dauern aber auch wahrscheinlich nicht lang zu fixen. Muss Niklas entscheiden, wie man damit umgeht. Wäre natürlich besser, wenns Quality Gate durchläuft