@spec active_subscription_for(Plausible.Auth.User.t()) ::
  Plausible.Billing.Subscription.t() | nil

@spec check_needs_to_upgrade(Plausible.Auth.User.t()) ::
  {:needs_to_upgrade, :no_trial | :no_active_subscription | :grace_period_ended}
  | :no_upgrade_needed

@spec format_price(Money.t()) :: String.t()

@spec has_active_subscription?(Plausible.Auth.User.t()) :: boolean()