Given a `List` model with the following associations:

```
has_many :list_group_memberships, dependent: :destroy
has_many :groups, through: :list_group_memberships
has_many :users, -> { unscope(:order).uniq }, through: :groups, source: :users

```

Basically I need to return the following but as an ActiveRecord::Relation, not an array:

```
def users
  super + [user]
end

```

Ideally, the `users` relation would use an `or` scope, but I can't work it out.