What attributes does NextCloud Contacts support?

I would like a comprehensive list of the attributes supported by https://github.com/nextcloud/contacts.git for https://github.com/FossifyOrg/Contacts/issues/85#issue-2144814636. Does this exist? If so, where is it located? If not, can anyone provide this information to me?

I expected that HowTo: Which attributes are used by Contacts app by default would provide this, but it does not appear to.