Workaround for /swagger not working

[utybo]

Because Swagger UI uses relative links to resolve resources (like CSS, JS and images), going to /swagger will serve the correct index.html file, but the browser will call the wrong URLs when trying to resolve resources. A simple workaround is to trigger a 307 redirection from /swagger to /swagger/index.html if possible.

There is a potential trap here because I don't think Ktor has an easy way of specifying "redirect to this subroute", and we can only set a redirection to an absolute path.