View Source ExTDLib.Object.StorePaymentPurposePremiumSubscription (ExTDLib v0.0.4)

The user subscribing to Telegram Premium.

Name	Type	Description
is_restore	bool	Pass true if this is a restore of a Telegram Premium purchase; only for App Store.
is_upgrade	bool	Pass true if this is an upgrade from a monthly subscription to early subscription; only for App Store.

More details on telegram's documentation.