Store comment sorting direction in user metadata

app/Core/Cache/CacheInterface.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace Kanboard\Core\Cache;
+
+/**
+ * Interface CacheInterface
+ *
+ * @package Kanboard\Core\Cache
+ * @author  Frederic Guillot
+ */
+interface CacheInterface
+{
+    /**
+     * Store an item in the cache
+     *
+     * @access public
+     * @param  string  $key
+     * @param  string  $value
+     */
+    public function set($key, $value);
+
+    /**
+     * Retrieve an item from the cache by key
+     *
+     * @access public
+     * @param  string  $key
+     * @return mixed            Null when not found, cached value otherwise
+     */
+    public function get($key);
+
+    /**
+     * Remove all items from the cache
+     *
+     * @access public
+     */
+    public function flush();
+
+    /**
+     * Remove an item from the cache
+     *
+     * @access public
+     * @param  string  $key
+     */
+    public function remove($key);
+}