fix(spaces): build correct URL to space in admin notification

In the process of promoting a user to a space admin, we send a
notification. This notification is not yet sent via novu, but fetched
via the `Notification` query.

To build the correct link in that notification, we use the space `name`,
which is its slug. Before this commit, we didn't fetch this property in
the query, which resulted in the link always being `/spaces/undefined`.

Refs: HOLI-9926