Hosting grafana using ingress-nginx behind a sub path

grafana-ingress.yaml

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /$1 
    nginx.ingress.kubernetes.io/use-regex: "true"
  name: grafana
  namespace: monitoring
spec:
  ingressClassName: nginx
  rules:
  - host: <your host>
    http:
      paths:
      - backend:
          service:
            name: grafana
            port:
              name: http
        path: /observe[/]?(.*)
        pathType: Prefix

grafana.ini

[server]
root_url: 'https://<your host>/observe/',
domain: 'prime.web.att.com',