Deleting a feed using REST API

My requirement is to clear all activities on a notification feed.

Based on this stackoverflow question I understand that there is an undocumented REST API to delete a feed and the dashboard truncate feed functionality uses it. I tried to replicate the call with the same parameters as dashboard:

DELETE /api/v1.0/feed/notification/f8fa1d12-594a-4b2b-ac58-23c912d1335a/?api_key=...&location=unspecified
Host: api.getstream.io
Authorization: notificationf8fa1d12-xxxx-xxxx-xxxx-23c912d1335a writetoken
stream-auth-type: simple
X-Stream-Client: stream-javascript-client-browser-unknown
Cache-Control: no-cache

Tried to use the same but am getting this error message:

{
  "code": null,
  "detail": "url signature missing or invalid",
  "duration": "6ms",
  "exception": "AuthenticationFailed",
  "status_code": 403
}

Is this the right way to use this API? I am using this from Java code and believe that the Java client doesn't have this functionality built in.