multiple file validation

/** ===== FILE: app\Http\Requests\validateFormDocument ====== */
public function rules()
{
  return [
   'caption.*' => 'required',
   'jenis.*' => 'required',
   'gambar.*' => 'required|image|mimes:jpeg,png,jpg,gif,svg|max:2048',
  ];
}

public function messages()
{
  // ??? Custom validation messages nya seperti apa..?
}

/** ===== FILE: app\Http\Controllers\Document ======= */

public function store(validateFormDocument $request)
{
  ...
}


/** ===== FILE: resources\views\form ======= */
<form id="formnya" method="POST" action="route('doc.store')" enctype="multipart/form-data">
  @csrf
  <input type="text" name="docname" >
  <!-- disini sebenarnya gambar bertambah ketika addRow button menggunakan Javascript
  tapi anggap saja gambar sudah ada di form.
  -->
  <div id="rowGambar">
   <div id="row_1">
    <input type="text" name="caption[]" >
    <input type="text" name="jenis[]" >
    <input type="file" name="gambar[]"
   </div>
   <div id="row_2">
    <input type="text" name="caption[]" >
    <input type="text" name="jenis[]" >
    <input type="file" name="gambar[]"
   </div>
   <div id="row_3">
    <input type="text" name="caption[]" >
    <input type="text" name="jenis[]" >
    <input type="file" name="gambar[]"
   </div>
  </div>
</form>