Add discount "restrictions" checkbox

[odin-h]

Problem

There is no way to distinguish between regular discounts and e.g. loyalty program-only deals.

Proposed solution

Add a checkbox that indicates that the discount have restrictions or may not apply for all customers and give the option to describe the type of restrictions that apply the discount when the checkbox is ticked.

Part of

• #172

[Showmaster3000]

This problem needs more discussion. There are different possibilities:

• product with discount for customer cards only -> two prices, but not for every customer
• product with discount for everybody and even more discount for customer cards -> we have three prices to add

Another thing is discount because of reaching the "best before" date - so single or some more items are sold cheaper instead of trashing it cause nobody buys it.

But both things make it more complex to fastly collect prices.