The old application has a `log` field in the `data` array of donations. The log contains all changes made through the backend (status changed, enabling write, deletions), and some status changes from the frontend: info when the external payment was booked, if the donation was canceled, parent and child IDs of paypal transactions.
The log is displayed in the backend and the cancellation log entry is used to generate the cancellation report.
While `DoctrineDonationRepository::updateDonationEntity` will preserve existing logs, there is no way to access the log from the frontend, so a domain object has to be createdthere must also be a way to write to the log when one of the cases above occurs.
Internal DB formatly, the of the log data is an array with timestamps (format `Y-m-d H:i:s') as keys and the log messages as values.