Disable sharing calendars via link when sharik via link is disabled

This mod disallows sharing calendars via link when `shareapi_allow_links`
is disabled.

Related: nextcloud/calendar#525
Related: nextcloud/calendar#4399
Author-Change-Id: IB#1126264
Signed-off-by: Pawel Boguslawski <pawel.boguslawski@ib.pl>

Author: pboguslawski

apps/dav/lib/CalDAV/CalDavBackend.php

@@ -3,6 +3,7 @@
  * @copyright Copyright (c) 2016, ownCloud, Inc.
  * @copyright Copyright (c) 2018 Georg Ehrke
  * @copyright Copyright (c) 2020, leith abdulla (<online-nextcloud@eleith.com>)
+ * @copyright Copyright (c) 2022 Informatyka Boguslawski sp. z o.o. sp.k., http://www.ib.pl/
  *
  * @author Chih-Hsuan Yen <yan12125@gmail.com>
  * @author Christoph Wurst <christoph@winzerhof-wurst.at>
@@ -497,6 +498,10 @@ public function getUsersOwnCalendars($principalUri) {
 	 * @return array
 	 */
 	public function getPublicCalendars() {
+		// Sharing via link must be enabled.
+		if ($this->config->getAppValue('core', 'shareapi_allow_links', 'yes') === 'no' ) {
+			return array_values([]);
+		}
 		$fields = array_column($this->propertyMap, 0);
 		$fields[] = 'a.id';
 		$fields[] = 'a.uri';
@@ -555,6 +560,10 @@ public function getPublicCalendars() {
 	 * @throws NotFound
 	 */
 	public function getPublicCalendar($uri) {
+		// Sharing via link must be enabled.
+		if ($this->config->getAppValue('core', 'shareapi_allow_links', 'yes') === 'no' ) {
+			throw new NotFound('Node with name \'' . $uri . '\' could not be found');
+		}
 		$fields = array_column($this->propertyMap, 0);
 		$fields[] = 'a.id';
 		$fields[] = 'a.uri';

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

@@ -1,6 +1,7 @@
 <?php
 /**
  * @copyright Copyright (c) 2016 Thomas Citharel <tcit@tcit.fr>
+ * @copyright Copyright (c) 2022 Informatyka Boguslawski sp. z o.o. sp.k., http://www.ib.pl/
  *
  * @author Christoph Wurst <christoph@winzerhof-wurst.at>
  * @author Georg Ehrke <oc.list@georgehrke.com>
@@ -205,6 +206,11 @@ public function httpPost(RequestInterface $request, ResponseInterface $response)
 				}
 			}
 
+			// Sharing via link must be enabled.
+			if ($this->config->getAppValue('core', 'shareapi_allow_links', 'yes') === 'no') {
+				return;
+			}
+
 			$node->setPublishStatus(true);
 
 			// iCloud sends back the 202, so we will too.