krileon wrote: [
So, each course should have a parent and its childs?
Probably, as it's your install you need to decide if the usage fits your design. Using parents is completely optional.
If so, what would be the difference between each parent?
Nothing except name, description, and what plans are set to be their child plans.
I did as you recommend, creating a parent with its children. But, how do you avoid people to subscribe only to the father, and not to a child. Parents don't have nothing, just descriptions, name, children. Can I restrict somehow to avoid people to subscribe to a parent without subscribing to a child?