Event Wizard: Require Tickets before Event Publishing

[kushthedude]

See fossasia/open-event-frontend#2482

Make sure Event has tickets available before Publishing

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[iamareebjamal]

Copied from PR:

The check has to be this way. The implementation may not be correct here, but frontend will have to change its implementation when the check is in place.

There is no way this check can be implemented without frontend changing its implementation, so let's stop using the excuse that frontend will break. It will in either case. Having a check on frontend is not enough.

The issue was created to prevent spam. There are no JavaScript crawler spam bots. They will always use API to spam. So, frontend check is useless.

Frontend will have to first add a draft event, create tickets and then publish event as discussed many times before. This will have to be the way due to the limitations of JSONAPI spec that does not support nested creation of items