Swapped back handling to instead be pre-determined instead of being
based upon session/referrer which would cause inconsistent results when
referrer data was not available (redirect to app-loaded images/files).
To support, this adds a mechansism to provide a URL through request
data.
Also cleaned up some imports in code while making changes.
Closes#4656.
Changes their endpoints and remove the user id from the URLs.
Simplifies list changes to share a single endpoint, which aligns it to
the behaviour of the existing sort preference endpoint.
Also added test to ensure user preferences are deleted on user delete.
