fix: use correct field values for source

Author: ju5t

src/Enums/Source.php

@@ -5,6 +5,7 @@
 enum Source: string
 {
     case Contact = 'contact';
-    case SalesInvoices = 'sales_invoices';
+    case SalesInvoice = 'sales_invoice';
+    case Estimate = 'estimate';
     case Identity = 'identity';
 }