Addressbooks should be check for uid conccurency before accepting a vcard

[skjnldsv]

Like calendars:

server/apps/dav/lib/CalDAV/CalDavBackend.php

Lines 978 to 990 in db941a3

	$q = $this->db->getQueryBuilder();
	$q->select($q->createFunction('COUNT(*)'))
	->from('calendarobjects')
	->where($q->expr()->eq('calendarid', $q->createNamedParameter($calendarId)))
	->andWhere($q->expr()->eq('uid', $q->createNamedParameter($extraData['uid'])));
	$result = $q->execute();
	$count = (int) $result->fetchColumn();
	$result->closeCursor();
	if ($count !== 0) {
	throw new \Sabre\DAV\Exception\BadRequest('Calendar object with uid already exists in this calendar collection.');
	}

• New db column
• Migration path