add missing @method having() in Model

add missing @method having() in Model

Author: paul45

system/Model.php

@@ -43,6 +43,7 @@
  * @method $this groupBy($by, ?bool $escape = null)
  * @method $this groupEnd()
  * @method $this groupStart()
+ * @method $this having($key, $value = null, ?bool $escape = null)
  * @method $this havingGroupEnd()
  * @method $this havingGroupStart()
  * @method $this havingIn(?string $key = null, $values = null, ?bool $escape = null)