How to allow a slow-response in Traefik 2+?

Question

I need to tell Treaefik to wait for a slow response from a server. I'm a little puzzled as the evidence I have is that there's a limit of 60 seconds that doesn't correspond to any default that I see in traefik.

I'm working in kubernetes.

I think that I should configure the transport used for the service (but I may be wrong, I have not really understood all the parameters). My attempt was:

apiVersion: traefik.containo.us/v1alpha1
kind: IngressRoute
...
spec:
  entryPoints:
  - websecure
  routes:
  - kind: Rule
    match: Host(`mydomain`) && PathPrefix(`/api`, `/static/`, `/admin`)
    middlewares:
    - name: do-buffering
    services:
    - name: wa-django
      port: 80
      serversTransport: slow-response
---
apiVersion: traefik.containo.us/v1alpha1
kind: ServersTransport
metadata:
  name: slow-response
  namespace: wa
spec:
    forwardingTimeouts:
      dialTimeout: "200s"

I read a message that suggests using terminationDelay as a service parameneter, but I can only see docs and an example for file-provider and not for Kubernetes (and kubectl explain doesn't show any such conf parameter).