Webhook to Google Chat

[Domearian]

Hi All,

I created a webhook into our company Google Chat. Added a simple BOT that when a new item is added, the process will run a custom task. A Webhook.

Settings:

Preset: Custom

URL: Copied from Webhook in Google Chat

HTTP Verb: POST

HTTP CONTENT TYPE: JSON

BODY: "HELLO"

That is it. When I test it, I get:

This is a closed webchat, so private to only the invitees. When I simply run the URL for the webhook it clearly displays that it is not Authorised: 

{
  "error": {
    "code": 401,
    "message": "API keys are not supported by this API. Expected OAuth2 access token or other authentication credentials that assert a principal. See https://cloud.google.com/docs/authentication",
    "status": "UNAUTHENTICATED",
    "details": [
      {
        "@type": "type.googleapis.com/google.rpc.ErrorInfo",
        "reason": "CREDENTIALS_MISSING",
        "domain": "googleapis.com",
        "metadata": {
          "method": "google.chat.v1.ChatService.ListMessages",
          "service": "chat.googleapis.com"
        }
      }
    ]
  }
}

 Surely it should be authorised using my credentials as the developer.