v5.0.0 update

app/Http/Controllers/V1/Admin/General/NumberPlaceholdersController.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace Crater\Http\Controllers\V1\Admin\General;
+
+use Crater\Http\Controllers\Controller;
+use Crater\Services\SerialNumberFormatter;
+use Illuminate\Http\Request;
+
+class NumberPlaceholdersController extends Controller
+{
+    /**
+     * Handle the incoming request.
+     *
+     * @param  \Illuminate\Http\Request  $request
+     * @return \Illuminate\Http\Response
+     */
+    public function __invoke(Request $request)
+    {
+        if ($request->format) {
+            $placeholders = SerialNumberFormatter::getPlaceholders($request->format);
+        } else {
+            $placeholders = [];
+        }
+
+        return response()->json([
+            'success' => true,
+            'placeholders' => $placeholders,
+        ]);
+    }
+}