Problem

The KB feature just won't work without OAuth with impersonation, and the error is misleading

Steps to reproduce the issue

1. Create an AppLinks between Jira and Confluence using OAuth (without impersonation).
2. Link a KB space with a Service Desk project and set to allow Only licensed users who have access to the space.
3. Configure the space permission accordingly in Confluence.
4. As a SD and Confluence licensed users, with absolute permission on the linked space, view a Service Desk issue and observe the Related knowledge base articles panel.

Expected result

The user can view suggested articles or given the option to create a new article

Actual result

• 
• in the browser developer tools > Network tab, there's a 403 error and the response -->

  {"errors":[{"errorMessage":"Can't return search results because of a problem with the Confluence space permissions. They might be misconfigured, or in conflict with the knowledge base settings in Service Desk. Ask a system admin to help you troubleshoot."}],"reasonKey":"sd.knowledge.base.applink.forbidden","reasonCode":"403"}
  

Workaround

Utilise OAuth with impersonation for AppLinks

Documentation related to this change can be found here. 

In particular, note: Check the servers have the same set of users, to configure using OAuth (with impersonation) authentication.