* Event cancellation: Add safety and security checks
When cancelling an event, a large sum of money might be refunded
instantly. This PR adds safety features around this by
- doing a dry-run first that shows a preview of the expected refund sum
- sending a confirmation mode via email for any automatic refunds of more than 100 currency units
- keeping a more detailed log of the settings this was executed with
* Update src/pretix/control/views/orders.py
Co-authored-by: luelista <weller@rami.io>
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Co-authored-by: luelista <weller@rami.io>
