According to multiple FastAPI discussions [1], FastAPI only includes a
built-in mechanism to redirect requests including a trailing slash, to
its variation without slash, using a `307` status code.
This can be an issue when certain clients do not send the same headers
on the redirected request.
This change adds a custom FastAPI `APIRouter`, that registers both route
path variations (with and without trailing slash), while only marking
the path without slash for being included in the OpenAPI schema.
[1] https://github.com/fastapi/fastapi/discussions/7298
