Store a user's preferences in a dedicated directory rather than in a single file

refs #5600

doc/installation.md

@@ -302,3 +302,8 @@ The first release candidate of Icinga Web 2 introduces the following non-backwar
 * The **instances.ini** configuration file provided by the monitoring module
   has been renamed to **commandtransports.ini**. The content and location of
   the file remains unchanged.
+
+* The location of a user's preferences has been changed from
+  **<config-dir>/preferences/<username>.ini** to
+  **<config-dir>/preferences/<username>/config.ini**.
+  The content of the file remains unchanged.

library/Icinga/User/Preferences/Store/IniStore.php

@@ -34,7 +34,7 @@ class IniStore extends PreferencesStore
     protected function init()
     {
         $this->preferencesFile = sprintf(
-            '%s/%s.ini',
+            '%s/%s/config.ini',
             $this->getStoreConfig()->location,
             strtolower($this->getUser()->getUsername())
         );