def create_changeset(struct, params \\ %{}) do
    struct
    |> cast(params, ~w(user_id))
    |> cast_assoc(:user)
    |> validate_required(~w(user_id)a)
  end

  def grant_changeset(struct) do
    struct
    |> cast(%{decision: true}, ~w(decision)a)
  end

  def revoke_changeset(struct) do
    struct
    |> cast(%{decision: false}, ~w(decision)a)
  end