- Introduced entities `ReiterController`, `HorseController`, and `VereinController`, with associated REST routes.
- Implemented upsert functionality for `Reiter`, `Horse`, and `Verein` repositories.
- Added services for `Altersklasse` calculations and integrated them into the domain layer.
- Updated database schema to include `ReiterTable`, `HorseTable`, `VereinTable`, and `FunktionaerTable`.
- Refactored `masterdataApiModule` to register new domain controllers.
- Adjusted Ktor server and Spring configurations to support new domains.
Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>