Update the UX to refer to structure direct chats as friends. The direct chats are pulled into their own tab in the space drawer.
The `UserDetailDialog` is also updated to check whether a direct chat already exists and if not ask to invite as friend.
Since this means that the space drawer can no longer be hidden when there are no spaces,
also make it less empty by adding a button for creating new spaces.
More things will come in the future.
BUG: 479051
