move customer_data field to metadata

Ref jazzband#378

payments/stripe/providers.py

@@ -130,7 +130,7 @@ def create_session(self, payment):
             if payment.billing_first_name or payment.billing_last_name:
                 session_data.update(
                     {
-                        "customer_data": {
+                        "metadata": {
                             "customer_name": f"{payment.billing_first_name} {payment.billing_last_name}"
                         }
                     }