We are on ArcGIS Enterprise 11.3 and dabbling with feature service webhooks for the first time. We have been able to successfully set them up and use them via the admin portal. ESRI documentation indicates that users not assigned the admin role should also be able to create feature service webhooks via the administrative API.
https://enterprise.arcgis.com/en/portal/latest/administer/windows/create-webhooks.htm

We have followed the disparate breadcrumbs across several pages to assign the proper privileges, generated a token to access the administrative API, but when sending a call to create a webhook we are receiving a 403 HTTP error which seems to indicate "Insufficient Permissions"
I will elaborate on our workflow thus far below.
https://developers.arcgis.com/rest/enterprise-administration/server/create-webhook/

In our test environment, we have configured a user with the Publisher role and assigned the Feature Layer privilege, the View All Content privilege, and the Publish server-based layers privilege. The user is the owner of the content for which we are attempting to create the webhook. The service has editing and change tracking enabled (without sync).
We generated a Client ID/Client secret and used these in order to generate a token using the OAUTH2 workflow (using the Authorize and Token endpoints as described below).
https://developers.arcgis.com/rest/users-groups-and-items/authentication/
https://developers.arcgis.com/rest/users-groups-and-items/authorize/
https://developers.arcgis.com/rest/users-groups-and-items/token/
We can successfully generate a token following these steps. Then when attempting to create a feature service webhook with the "Create" endpoint, we're getting the 403 HTTP error, which seems to indicate "Insufficient Permissions". Below is the URL format that we are using
https://<root>/services/Placehloder_serviceName/FeatureServer/webhooks/create
As far as I can tell, we have followed the workflow as prescribed. What additional steps can we take to try to get the API to successfully create a webhook?
(and while we're talking feature service webhooks, I'll just say that you should be able to set these up directly from the Settings page of the feature service if you are the content owner. Requiring an admin or a complicated multi-part api process is too cumbersome for something like this.)