Contact could not be saved if both anniversary and birthday

[ghost]

Steps to reproduce

1. Create a new contact
2. Add birthday
3. Add anniversary

---

1. Edit an existing contact that has a birthday
2. Add anniversary

Expected behaviour

Save contact.

Actual behaviour

Error message: "Contact could not be saved."

Browser log

"Calendar object with uid already exists in this calendar collection."

[christian-weiss]

@pinowthebird i have a very similar issue in #507 and some findings. Can you confirm my findings with your issue?

[ghost]

Yes, and I'm pretty sure the issue comes down to "more than one date field for a contact". So the same goes for date of death as well.