add carddav-search option for X-ADDRESSBOOKSERVER-MEMBER

Adding field X-ADDRESSBOOKSERVER-MEMBER
which can be used to relate persons to groups (macos behaviour).

- groups are cards with field X-ADDRESSBOOKSERVER-KIND == 'group'
- and all members' UUID/URI in the X-ADDRESSBOOKSERVER-MEMBER array of that group-card.

Signed-off-by: labor4 <schreibtisch@labor4.ch>

apps/dav/lib/CardDAV/AddressBookImpl.php

@@ -269,7 +269,7 @@ class AddressBookImpl implements IAddressBook {
 				}
 
 			// The following properties can be set multiple times
-			} else if (in_array($property->name, ['CLOUD', 'EMAIL', 'IMPP', 'TEL', 'URL'])) {
+			} else if (in_array($property->name, ['CLOUD', 'EMAIL', 'IMPP', 'TEL', 'URL', 'X-ADDRESSBOOKSERVER-MEMBER'])) {
 				if (!isset($result[$property->name])) {
 					$result[$property->name] = [];
 				}