Allow deliveries without purchase

[alehaa]

Sometimes there can be deliveries with no specific purchase. An example would be waranty hardware replacements. I therefore suggest making Delivery.purchase an optional field.

[matejv]

The code that handles asset import from CSV would have to account for this. It can automatically create new purchases and deliveries if a matching one does not exist yet.

Other than that it should be fairly straightforward to do.

[matejv]

Should a Delivery without purchase have a Supplier or not? Do we need to add Delivery.supplier field?

[alehaa]

Hmm. Good point, I hadn't thought of that. It would make sense to have a supplier, since someone has to send the parts.

Perhaps another (and cleaner) way to implement this would be to use purchases linked to the warranty case instead of having a price attached? However, in this case I think we should add an option to select a manufacturer instead of a supplier for the purchase if the hardware is shipped directly from the manufacturer?