Feat: Add Swagger API documentation (#158)

* Add OpenAPI/Swagger documentation for web api #111

* Improve descriptions and add examples where possible

* Adjust API documentation #111

* Add error responses

Co-authored-by: Angelo Capossele <angelocapossele@gmail.com>
Co-authored-by: Jake Cahill <45230295+JakeSCahill@users.noreply.github.com>
Co-authored-by: Wolfgang Welz <welzwo@gmail.com>