POST: 403 error in REST
Do you provide a (Basic) authorization header, as well as a X-CSRF-Token header in your POST?

See also:
https://www.drupal.org/documentation/modules/rest/start - "2.2 Unsafe methods &amp; CSRF protection: X-CSRF-Token request header"

Edit:
So you should at least specify the following HTTP headers:


Content-type: application/json
X-CSRF-Token: [TOKEN RETURNED FROM A REQUEST TO /rest/session/token]