This feature introduces a breaking change, that restricts the User's that
can create/edit/delete Articles to only those that have the `admin` Role.
Fixed ESLint issues.
Resolved merge conflicts, and moved new client Article Service
`createOrUpdate` functionality to new Admin feature controller.
Removed edit functionality from client-side Article controller.
Adds an additional check for the existence of a populated user
reference, when determining if the current user has immediate access to
the requested article.
Without this fix, the server will throw an error if the requested
article doesn't have a populated user field.
Modified the article & articles list view's to check if the article has
a populated user. If not, then it will display "Deleted User" in place
of the missing user reference.
Added a server-side test that ensures we can get a single article if
the article.user field is referencing a deleted user.
Fixes#1082
