* use numbers and not http.Status___ enum

* fix test

* add many missing swagger responses

* code format

* Deletion Sould return 204 ...

* error handling improvements

* if special error type ... then add it to swagger too

* one smal nit

* invalidTopicsError is []string

* valid swagger specification 2.0
 - if you add responses swagger can tell you if you do it right 👍

* use ctx.InternalServerError

* Revert "use numbers and not http.Status___ enum"

This reverts commit b1ff386e24.

* use http.Status* enum everywhere