fix(gui) default the API Server to request URL minus "/gui"

[nickolaev]

Signed-off-by: Nikolay Nikolaev nikolay.nikolaev@konghq.com

Summary

Make kuma-gui API server to default to request URL minus "/gui"

Issues resolved

Fix #943

Imports the changes from kumahq/kuma-gui#54

Tested with Kong Ingress as follows:

$  kubectl apply -f https://bit.ly/k4k8s

$  echo '
  apiVersion: networking.k8s.io/v1beta1
  kind: Ingress
  metadata:
    name: demo
    namespace: kuma-system
    annotations:
      konghq.com/strip-path: "true"
  spec:
    rules:
      - http:
          paths:
            - path: /
              backend:
                serviceName: kuma-control-plane
                servicePort: 5681
    ' | kubectl apply -f -


$  echo '
  apiVersion: networking.k8s.io/v1beta1
  kind: Ingress
  metadata:
    name: demo
    namespace: kuma-system
    annotations:
      konghq.com/strip-path: "false"
  spec:
    rules:
      - http:
          paths:
            - path: /config
              backend:
                serviceName: kuma-control-plane
                servicePort: 5681
    ' | kubectl apply -f -