Started addition of favourite system

app/Actions/Favourite.php

@@ -0,0 +1,17 @@
+<?php namespace BookStack\Actions;
+
+use BookStack\Model;
+use Illuminate\Database\Eloquent\Relations\MorphTo;
+
+class Favourite extends Model
+{
+    protected $fillable = ['user_id'];
+
+    /**
+     * Get the related model that can be favourited.
+     */
+    public function favouritable(): MorphTo
+    {
+        return $this->morphTo();
+    }
+}