Add validity option to modify product / ticket

[mariobehling]

After an organizer creates a ticket there are a number of options to specify the ticket properties. One option is to change the validity of a ticket. This is relevant if an event runs over several days and has a day ticket. The validity of a day ticket would be for example day 2.

Other platforms like Pretix have a similar option already.

Implement the validity option for products / tickets as in the screenshot below. Also add endpoints for invalid_time. Compare to https://docs.pretix.eu/dev/api/resources/checkin.html#checking-a-ticket-in

[Shubham-Khetan-2005]

I want to work on this issue please assign me