BR-WG3-030 Subscription modification

Responsible	@Hanna Kucherova (Unlicensed)
Responsible Team	WG3
Priority	MUST HAVE
Status	NEW
Description	The system should allow Users to change their current Subscription package to another one offered by the creator.
Extra Information	After successful payment, the new subscription should be activated and the old one deactivated.
Related BRs	BR-WG3-030 Subscriptions Overview
Related Processes	BP-WG3-030 Subscriptions management