Write WordPress plugin called "studiou-wc-mandatory-products" in PHP, that extends WooCommerce plugin.
Plugin will have following features:

1. Extends Product Category editor (in menu Product/Categories) to allow to add mandatory products, that will be automatically added to cart when product from current product category will be added.
	- can be used in Parent category, and all child categories will have this same feature also (will be inherit this settings) 
	- desired mandatory product for automatic add to cart can be add only one time (in cart) or only one time for product (types: 'OnePerCart', 'OnePerProduct').
	- extends DB structure or use existing to store this settings
2. When I select product and press Add to Cart button, then if product category (where selected product belongs) has settings for mandatory associated product, then associated product will be added to cart also (together, as specified at 1.)
3. Add information in Product editor, that product has mandatory product set (if any)


Sample scenario:

Product categories tree
	- Main Category
		- SubCategory1
		- SubCategory2
		
Products
	- MandatoryProduct1 (In Main Category)
	- ProductA (In SubCategory1)
	- ProductB (In SubCategory2)
	
Settings
	Main Category
		Mandatory Products: MandatoryProduct1, amount: 1, type: OnePerCart
		
		
User Ordering:
	- Add to cart ProductA amount:10pcs
	- Add to cart ProductB amount:2pcs
	- Shows cart:
		ProductA 10pcs
		ProductB 2pcs
		MandatoryProduct1 1pcs