Started interface user shortcut form interface

Built controller actions and initual UI.
Still needs JS logic for shortcut input handling.

app/Settings/UserShortcutMap.php

@@ -0,0 +1,82 @@
+<?php
+
+namespace BookStack\Settings;
+
+class UserShortcutMap
+{
+    protected const DEFAULTS = [
+        // Header actions
+        "home_view" => "1",
+        "shelves_view" => "2",
+        "books_view" => "3",
+        "settings_view" => "4",
+        "favourites_view" => "5",
+        "profile_view" => "6",
+        "global_search" => "/",
+        "logout" => "0",
+
+        // Common actions
+        "edit" => "e",
+        "new" => "n",
+        "copy" => "c",
+        "delete" => "d",
+        "favourite" => "f",
+        "export" => "x",
+        "sort" => "s",
+        "permissions" => "p",
+        "move" => "m",
+        "revisions" => "r",
+
+        // Navigation
+        "next" => "ArrowRight",
+        "previous" => "ArrowLeft",
+    ];
+
+    /**
+     * @var array<string, string>
+     */
+    protected array $mapping;
+
+    public function __construct(array $map)
+    {
+        $this->mapping = static::DEFAULTS;
+        $this->merge($map);
+    }
+
+    /**
+     * Merge the given map into the current shortcut mapping.
+     */
+    protected function merge(array $map): void
+    {
+        foreach ($map as $key => $value) {
+            if (is_string($value) && isset($this->mapping[$key])) {
+                $this->mapping[$key] = $value;
+            }
+        }
+    }
+
+    /**
+     * Get the shortcut defined for the given ID.
+     */
+    public function getShortcut(string $id): string
+    {
+        return $this->mapping[$id] ?? '';
+    }
+
+    /**
+     * Convert this mapping to JSON.
+     */
+    public function toJson(): string
+    {
+        return json_encode($this->mapping);
+    }
+
+    /**
+     * Create a new instance from the current user's preferences.
+     */
+    public static function fromUserPreferences(): self
+    {
+        $userKeyMap = setting()->getForCurrentUser('ui-shortcuts');
+        return new self(json_decode($userKeyMap, true) ?: []);
+    }
+}