Add Spendenbescheinigung

[lislis]

Treasurers should be able to track donation receipts.
They check the banking account, see that there was a donation and can add it to the receipt to do list in the app.
We need:

• date of the donation
• id (given by us)
• (something that helps identifying the donation?)
• amount
• checkbox receipt was filled out
• date of receipt was filled out
• checkbox board member has singed
• date board member has signed
• checkbox receipt was sent out
• date receipt was sent out

Anything else