I'm selling licensplates for cars. These licensplates comes in 8 variants.
How do I make these variants?
When a costumer buy a set of licensplates, he has to write 7 letters/numbers. This combination of letters/numbers must then ONLY be able to order ONCE. How do I make this?
Example: When a set of licensplates with [AB12345] is ordered, another costumer may NOT be able to order this combination!