Bug: Invalid top-level self link

[bart-degreed]

Description

When requesting the url https://localhost/api/v3/users/123, a response is returned with top-level self link https://localhost/api/v3/users.

From the JSON:API spec:

The top-level links object MAY contain the following members:
- self: the link that generated the current response document.

This may be related to #632, but in this case it involves an existing resource.