[Enhance] API for purchases, items, operations

- Add API endpoints for purchases, items, and operations
- Header checker? :)

latest version/server/course.py

@@ -19,7 +19,7 @@ def course_me(user_id):
         user = UserOnline(c, user_id)
         core = ItemCore(c)
         core.item_id = 'core_course_skip_purchase'
-        core.select(user)
+        core.select_user_item(user)
         x = UserCourseList(c, user)
         x.select_all()
         return success_return({