Add a group-buying page where a shop user lists, creates, edits, and deletes
its own activities, configuring the SKU, localized name and description, group
price, required paid members, active window, and group lifetime, and seeing each
activity's open groups. Expose it as a group-buying navigation entry.
Add a flash-sale page where a shop user lists, creates, edits, and deletes its
own sessions and their SKU activity items, setting the fixed sale price,
currency, reserved stock, and per-customer limit. Expose it as a flash-sale
navigation entry beside the existing shop operations.
Add a coupons page where a shop user lists, creates, edits, enables/disables,
and deletes only its own templates, with localized titles, minor-unit discount
and threshold, currency, claim stock, and an active window. Expose it as a
coupons navigation entry beside the existing shop operations.