feat(custom-field): tambahkan fitur custom field

- Menambahkan model CustomField dengan atribut mass assignable.
- Membuat request validation untuk custom field.
- Menambahkan route dan breadcrumb untuk custom field.
- Membuat migration untuk tabel custom_fields.
- Menambahkan export functionality untuk custom field.
- Membuat view untuk menambah dan mengedit custom field.

app/Exports/CustomFieldExport.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace Modules\Lpj\Exports;
+
+use Maatwebsite\Excel\Concerns\FromCollection;
+use Maatwebsite\Excel\Concerns\WithColumnFormatting;
+use Maatwebsite\Excel\Concerns\WithHeadings;
+use Maatwebsite\Excel\Concerns\WithMapping;
+use Modules\Lpj\Models\CustomField;
+use PhpOffice\PhpSpreadsheet\Style\NumberFormat;
+
+class CustomFieldExport implements WithColumnFormatting, WithHeadings, FromCollection, WithMapping
+{
+    public function collection()
+    {
+        return CustomField::all();
+    }
+
+    public function map($row): array
+    {
+        return [
+            $row->id,
+            $row->name,
+            $row->type,
+            $row->created_at,
+            $row->updated_at,
+        ];
+    }
+
+    public function headings(): array
+    {
+        return [
+            'ID',
+            'Name',
+            'Type',
+            'Created At',
+            'Updated At',
+        ];
+    }
+
+    public function columnFormats(): array
+    {
+        return [
+            'A' => NumberFormat::FORMAT_NUMBER,
+            'D' => NumberFormat::FORMAT_DATE_DDMMYYYY,
+            'E' => NumberFormat::FORMAT_DATE_DDMMYYYY,
+        ];
+    }
+}