We get this from validation errors such as this:

<?xml version="1.0"?>
<d:multistatus xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns" xmlns:cal="urn:ietf:params:xml:ns:caldav" xmlns:cs="http://calendarserver.org/ns/" xmlns:card="urn:ietf:params:xml:ns:carddav">

<d:response>
  <d:href>/dav/addressbooks/christian.mollekopf@nestle.kolab.ch/8c0a369c-12ed-4fb4-a23b-a599d4e24001/d08178b1-3f3d-4576-a006-3ec50347432f.vcf</d:href>
  <d:propstat>
    <d:prop>
      <d:getetag>"596742e53dbebc4d-3"</d:getetag>
      <card:address-data>BEGIN:VCARD&#xD;

VERSION:3.0&#xD;
PRODID:-KolabiRony DAV Server 0.4.3SabreSabre VObject 4.5.7//EN&#xD;
UID:d08178b1-3f3d-4576-a006-3ec50347432f&#xD;
FN:lasdjfldsjf&#xD;
EMAIL;TYPE=INTERNET,HOME:emptyfn@example.com&#xD;
REV:20250502T020304Z&#xD;
END:VCARD&#xD;
</card:address-data>

    </d:prop>
    <d:status>HTTP/1.1 200 OK</d:status>
  </d:propstat>
</d:response>

</d:multistatus>

[2025-07-16 16:01:49] production.DEBUG: C: PUT: http://imap/dav/addressbooks/user/christian.mollekopf@nestle.kolab.ch/eecdc229-4cd5-46cb-94c1-d3b37d4d688e/d08178b1-3f3d-4576-a006-3ec50347432f.vcf
Content-Type: text/vcard; charset=utf-8

BEGIN:VCARD
VERSION:3.0
PRODID:-KolabiRony DAV Server 0.4.3SabreSabre VObject 4.5.7//EN
UID:d08178b1-3f3d-4576-a006-3ec50347432f
FN:lasdjfldsjf
EMAIL;TYPE=INTERNET,HOME:emptyfn@example.com
REV:20250502T020304Z
END:VCARD

[2025-07-16 16:01:49] production.DEBUG: S: [403]
Date: Wed, 16 Jul 2025 16:01:49 GMT
Connection: Upgrade
Upgrade: h2c
Alt-Svc: h2c=":11080"
Cache-Control: no-cache
Content-Type: application/xml; charset=utf-8
Content-Length: 210

<?xml version="1.0" encoding="utf-8"?>
<D:error xmlns:D="DAV:" xmlns:C="urn:ietf:params:xml:ns:carddav">

<C:valid-address-data/>
<D:responsedescription>Failed restriction checks</D:responsedescription>

</D:error>