Separate routing logic and business logic

[RDIL]

Fixes #337

[LennardF1989]

I'll pull this in end-of-the-day and give it a checkup. Just to make sure I validate it accordingly: where does routing logic end in your opinion and where does business logic start? If I hear this, I would say the implementation of endpoints should only ever call other functions, that do stuff, and the only thing the endpoint does is return that or decide on the appropriate statuscode. Meaning that endpoint implementations are very small and compherensible functions to eventually return a response.

Is that how you see it, too?

[RDIL]

Yeah, that’s basically my philosophy. Endpoints only validate then call another function.

I tested this PR with Neko, all 3 game versions have no regressions.