Our donation entries can be soft-deleted from the Fundraising Operation Center as part of moderation efforts. Currently, we are mis-using the status field as a marker for soft-deletion (setting it to the string "D"). To properly separate the overloaded status field from the soft-delete function, we should add a dedicated field for the soft-deletion status

Acceptance Criteria

• The spenden table has a new field for soft-deletion
• Deleting a donation sets the field value
• The field value "survives" the round-trip of converting the database entity to a domain entity and back.
• We have a database migration that adds the new column