Let a shop purchase or event registration auto-add the user to a group with access to certain pages

This would be useful in allowing shop purchases and event registrations to automatically grant users access to certain pages by adding them to predefined groups (similar to the member/non-member access function, just not for member status). This would create or link a user account on successful payment or registration, assign them to the appropriate group, and unlock the related content immediately (cutting out the need to email them individually as registrations come through). Would help us as an association that sells access to recording and resource packs from prior PD events, which we would like to be able to provide as embedded youtube videos and downloadables on a web page requiring them to be logged in as the registering user. Ideally we could have a Resources -> My resources menu item which would then show anything they have purchased/have access to a child menu item/page.