Add missing webhook url field

[rocktavious]

Resolves #

Problem

The new endpoint integration doesn't expose the webhook url to send events to

Solution

Add that as a computed field so the customer can get at it and use it

Checklist

• I have run this code, and it appears to resolve the stated issue.
• This PR does not reduce total test coverage
• This PR has no user interface changes or has already received approval from product management to change the interface.
• Make a changie entry that explains the customer facing outcome of this change

[davidbloss]

Good catch!