properly mark birthday calendars as not shareable for now

Signed-off-by: Georg Ehrke <developer@georgehrke.com>

apps/dav/lib/CalDAV/Calendar.php

@@ -363,7 +363,11 @@ class Calendar extends \Sabre\CalDAV\Calendar implements IShareable {
 		return $this->caldavBackend->getPublishStatus($this);
 	}
 
-	private function canWrite() {
+	public function canWrite() {
+		if ($this->getName() === BirthdayService::BIRTHDAY_CALENDAR_URI) {
+			return false;
+		}
+
 		if (isset($this->calendarInfo['{http://owncloud.org/ns}read-only'])) {
 			return !$this->calendarInfo['{http://owncloud.org/ns}read-only'];
 		}

apps/dav/lib/CalDAV/Publishing/PublishPlugin.php

@@ -126,7 +126,10 @@ class PublishPlugin extends ServerPlugin {
 			});
 
 			$propFind->handle('{'.self::NS_CALENDARSERVER.'}allowed-sharing-modes', function() use ($node) {
-				return new AllowedSharingModes(!$node->isSubscription(), !$node->isSubscription());
+				$canShare = (!$node->isSubscription() && $node->canWrite());
+				$canPublish = (!$node->isSubscription() && $node->canWrite());
+
+				return new AllowedSharingModes($canShare, $canPublish);
 			});
 		}
 	}