Fix test result donor calculation (EXPOSUREAPP-5814) #2630

* Create new entires in TestDonorSettings

* Lint

* Improve logging

* Add some tests

* More tests and more logs

* Docs

* Use aggregated date

* Log right date

* Use `RiskLevelResult.lastRiskEncounterAt`

* Add unit tests.

* Tweak logging.

Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>
Co-authored-by: Matthias Urhahn <matthias.urhahn@sap.com>
Co-authored-by: Ralf Gehrer <ralfgehrer@users.noreply.github.com>