don't generate tickets for unpaid orders

[alexsavio]

[artcz]

Note: Tickets are tied to OrderItems, but OrderItem.ticket field is nullable, so we could potentially create Order with OrderItems and later backfill Tickets on the last page of the cart (order confirmation).

[matrixise]

I am going to associate this issue to ep2020

[umgelurgel]

This would definitely be a good issue to work on - but it's too big a change to fit in for this year; it's definitely out of scope for 2020, I'll mark it for 2021 though.