How to replace variables using Grizzly and Jsonnet

[srikarduplo]

I have requirement to dynamically pass the webhook. I created a jsonnet file with below.
I am able to call jsonnet --ext-str SLACK_WEBHOOK="$SLACK_WEBHOOK" temp2.jsonnet > output2.json and see the proper formatted Grizzly resource. How can I achieve the same with Grizzly commands I am looking for something like grr apply -ext-str SLACK_WEBHOOK="$SLACK_WEBHOOK" temp2.jsonnet

local webhook = std.extVar('SLACK_WEBHOOK');

{
  local contact(name, webhook) = {
    apiVersion: 'grizzly.grafana.com/v1alpha1',
    kind: 'AlertContactPoint',
    metadata: {
      name: name,
    },
    spec: {
      name: name,
      settings: {
        url: webhook,
      },
      disableResolveMessage: false,
      type: 'slack',
      uid: name,
    },
  },

  contact_points: [
    contact('slack', webhook),
  ],
}