Previously the links generated by the ReviewGroupUser resource

pointed at the UserResource. In other words, the delete link for the

ReviewGroupUser resource would actually be the delete link for the

UserResource and using it would result in the deletion of the user,

not the removal from review group. This was because these resources

shared a name (user) and as such, the lookups for URL names were

incorrect.
Now we correctly generate the links for the ReviewGroupUser resource.

We have added a related link to the actual user resource. Unit tests

have been added which ensure the delete links are correct in the

resources.

Ran unit tests.