store: postgres
key=k-2  amount 1999               -> HTTP 201  replayed=-    retry-after=-    {"id":1,"customer":"cus_42","amount":1999,"currency":"INR"}
key=k-2  amount 2999               -> HTTP 422  replayed=-    retry-after=-    {"title":"Idempotency-Key was already used with a different request","status":422}
key=k-2  same JSON, extra spaces   -> HTTP 422  replayed=-    retry-after=-    {"title":"Idempotency-Key was already used with a different request","status":422}
key=k-3  amount 2999               -> HTTP 201  replayed=-    retry-after=-    {"id":2,"customer":"cus_42","amount":2999,"currency":"INR"}
payments in the table: 2