integrate create billplz bill with create booking payment, and a new billplz callback url

config/billplz.php

@@ -3,7 +3,9 @@
 return [
     'base_url' => env('BILLPLZ_BASE_URL', 'https://www.billplz-sandbox.com'),
     'api_key' => env('BILLPLZ_API_KEY', '0fa4c710-761b-4a7a-a501-c2c2d02643d5'),
+    'x_signature_key' => env('BILLPLZ_X_SIGNATURE_KEY', 'S-pbNVthVRsvnPfZlgLwqqOg'),
     'collection_id' => env('BILLPLZ_COLLECTION_ID', 'hev2wdjy'),
+    'redirect_url' => env('BILLPLZ_REDIRECT_URL', 'localhost'),
     'callback_url' => env('BILLPLZ_CALLBACK_URL', 'localhost'),
     'maybank' => 'MB2U0227',
     'cimb' => 'BCBB0235'