Added very basic authorization.

app/Booking.php

@@ -118,4 +118,13 @@ class Booking extends Model
     public static function firstDate() {
         return Booking::min('date');
     }
+    
+    /**
+     * Get the date of the last booking.
+     *
+     * @return string
+     */
+    public static function lastDate() {
+        return Booking::max('date');
+    }
 }