v5.0.0 update

app/Http/Controllers/V1/Admin/RecurringInvoice/RecurringInvoiceFrequencyController.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Crater\Http\Controllers\V1\Admin\RecurringInvoice;
+
+use Crater\Http\Controllers\Controller;
+use Crater\Models\RecurringInvoice;
+use Illuminate\Http\Request;
+
+class RecurringInvoiceFrequencyController extends Controller
+{
+    public function __invoke(Request $request)
+    {
+        $nextInvoiceAt = RecurringInvoice::getNextInvoiceDate($request->frequency, $request->starts_at);
+
+        return response()->json([
+            'success' => true,
+            'next_invoice_at' => $nextInvoiceAt,
+        ]);
+    }
+}