Limit purchases by supplier

Currently, when creating a purchase order, you are able to select any supplier and from that supplier any product present in your product list. This applies even if the specific supplier you selected, does not supply at all that specific item. 

Ideally, to avoid mistakes, you should be able to link what products are purchasable from specific suppliers only. This way, when selecting a supplier, only the available list of items purchasable from that supplier will appear.