+ # Remove *user* from the DAViCal database. This should remove him
+ # from _every_ table in which he is referenced. Fortunately, DAViCal
+ # uses foreign keys properly (and only supports postgres, where they
+ # work!), so we can let the ON DELETE CASCADE trigger handle most of
+ # the work.
+ #
+ # @param user [User] the user to remove.
+ #
+ def remove_user(user)
+ raise NonexistentUserError.new(user.to_s()) if not user_exists(user)