Add SubscriptionStepsController to handle subscription steps

app/Http/Controllers/SubscriptionStepsController.php

@@ -0,0 +1,25 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Livewire\BillingPortal\Purchase;
+use Illuminate\Http\JsonResponse;
+
+class SubscriptionStepsController extends BaseController
+{
+    public function index(): JsonResponse
+    {
+        // @todo: perhaps integrate this in statics
+
+        $dependencies = collect(Purchase::$dependencies)
+            ->map(fn($dependency) => [
+                'id' => $dependency['id'],
+                'dependencies' => collect($dependency['dependencies'])
+                    ->map(fn($dependency) => Purchase::$dependencies[$dependency]['id'])
+                    ->toArray(),
+            ])
+            ->toArray();
+
+        return response()->json($dependencies);
+    }
+}