We only want to render the account link and login items in the header.
And we want only render the Multitenancy and Administrators sections in
the admin sidebar.
We include the administrators management so it's possible to give
permissions to other users to manage tenants.
In order to restrict access to other sections by typing the URL or
following a link, we're only enabling the rest of the routes when we
aren't in the multitenancy management mode.
In the management section, `current_user` is the user impersonated by
the manager. We were deciding whether to show the admin menu depending
on the privileges of the current user, but this menu should be shown
according to the privileges of the manager who is impersonating the
user.
We're doing a similar (very subtle) change in the login items. We were
rendering the `login_items` partial passing `current_user: user`.
However, inside this method, we were using `user_signed_in`, which
ignored the `current_user` we were passing. The result was always the
same expect in tests where we manually sign in users, but we're changing
it anyway in order to reduce confusion.
This way it's easier to refactor it.
Note we're using `with_request_url` in the tests because the component
renders the locale switcher, which needs a URL in order to work. This
doesn't affect whether we're in the management section or not.
