Allow custom date types

[S74HK9hV]

Is your feature request related to a problem? Please describe.
Contacts app only allows BIRTHDAY, ANNIVERSARY, DATE OF DEATH as milestone dates for a contact. But there are potentially other milestones that users may want to track. For example, graduation date, or date of becoming a citizen, etc.

Describe the solution you'd like
Allow user to add a event date with a custom label. In the drop down menu select CUSTOM DATE and then allow user to change the label and select the date. Google contacts has this feature already. Implementation details are below

For example, in the screenshot below, user should be able to add a custom event. The field would show "Custom Event" (instead of Date of death). User clicks on field name, and can change to any other event name

Describe alternatives you've considered
none

Additional context
Add any other context or screenshots about the feature request here.

Nextcloud 15 - only 3 date types available, birthday, anniversary, death

Google Contacts - user can add a date, then make a custom label for that date

[nextcloud-bot]

GitMate.io thinks possibly related issues are #672 (possibility to add custom instant messaging types), #518 (CardDav types), #55 (Allow vCard importing into custom AddressBook), #625 (Allow to set a date without a year), and #290 (Phone number type not shown when custom).

[skjnldsv]

Duplicate of #223