Admin console access

As a system administrator, I can access a dedicated UI for administering my Nuxeo instances

Context:
Authentication happens in the same way as usual with the regular login page, but we want a dedicated app that will be different from Web UI. It will be only available for administrators.

AC
A dedicated UI is available for administering a Nuxeo cluster
It is served on a dedicated URL (e.g., nuxeoadmin - nxadmin is already used by JSF UI)

If I am not logged in yet, I am redirected to the standard authentication page

UI is only loaded if I am someone granted access to it (as per https://doc.nuxeo.com/rest-api/1/management-endpoint/#authentication, only administrators and / or dedicated users can use the corresponding APIs), otherwise an error is shown