How can I setup a webhook for the google calendar api?
I'm currently making a post to the api, stating the webhook/ address https://us-central1-pushmessage-bd1eb.cloudfunctions.net/getUsers
axios({
    method: "POST",
    url:
        "https://www.googleapis.com/calendar/v3/calendars/xxx/events/watch",
    headers: {
        "Access-Control-Allow-Origin": "*",
        "Content-Type": "application/json;charset=UTF-8",
        Authorization: token.token_type + " " + token.access_token,
        "Content-Type": "application/json"
    },
    data: {
        id: "tester",
        type: "web_hook",
        address: "https://xxx.cloudfunctions.net/getUsers"
    }
})
However, I get the error:
  code: 401,
  message: 'Unauthorized WebHook callback channel: https://us-central1-xxx.cloudfunctions.net/getUsers' }
How can I verify the domain of my cloud function?
I have tried this method but still get the 401:
