[Bug]: (apps/dav) oc_cards_properties value is too short for contact categories

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Cards property value is limited to 255 chars, it is too short for contact categories field.

Categories truncated so searching attendees in calendar for example returns random results depending on which groups truncated

Steps to reproduce

1. add contact to a quite big number of groups with long names, so CATEGORIES field exceed 254 chars
2. try to add group attendee from calendar app
3. there is probability that required group was truncated and it fails to find all group members

Expected behavior

It adds all group members as attendee

Nextcloud Server version

31

Operating system

Other

PHP engine version

PHP 8.4

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

I was able to work it around by altering table to 4095 chars and modifying restriction in this line: https://github.com/nextcloud/server/blob/ddc272402dd5c8d220b65c7bfafd0bc1509f6f6d/apps/dav/lib/CardDAV/CardDavBackend.php#L1399

Maybe it needs more proper solution because of number of groups can be big enough.

Start in apps/dav/lib/CardDAV/CardDavBackend.php around line 1399 and inspect how oc_cards_properties stores the CATEGORIES value. Reproduce the issue with contacts having long category lists, then verify that the chosen fix preserves all categories and allows calendar attendee searches to find every group member.