Add config to sharemanager

lib/private/share20/manager.php

@@ -1111,6 +1111,13 @@ class Manager implements IManager {
 		return $this->config->getAppValue('core', 'shareapi_only_share_with_group_members', 'no') === 'yes';
 	}
 
+	/**
+	 * Check if users can share with groups
+	 * @return bool
+	 */
+	public function allowGroupSharing() {
+		return $this->config->getAppValue('core', 'shareapi_allow_group_sharing', 'yes') === 'yes';
+	}
 
 	/**
 	 * Copied from \OC_Util::isSharingDisabledForUser

lib/public/share/imanager.php

@@ -220,6 +220,13 @@ interface IManager {
 	 */
 	public function shareWithGroupMembersOnly();
 
+	/**
+	 * Check if users can share with groups
+	 * @return bool
+	 * @since 9.0.1
+	 */
+	public function allowGroupSharing();
+
 	/**
 	 * Check if sharing is disabled for the given user
 	 *