Stripe Subscription with Billing cycle anchor does not apply discounts on initial invoice

README.md

I am creating a subscription with billing_cycle_anchor set to first day of next month. Below is the params passed when creating subscription

{
  "metadata": {
    "tenant_id": "2cf19732-0c7b-42e4-a0a2-90fd9c0e7111"
  },
  "collection_method": "send_invoice",
  "days_until_due": "30",
  "backdate_start_date": "1645171200",
  "items": {
    "0": {
      "quantity": "1",
      "price": "price_1KVX9cBuQq6cUmE7iODbojye",
      "tax_rates": {
        "0": "txr_1KVKHvBuQq6cUmE7lvmOUWU2"
      }
    }
  },
  "billing_cycle_anchor": "1646121600",
  "customer": "cus_LBwT8BBsUSTO3S"
}

// Invoke subscription API as
Subscription.create(params)

I am creating coupon by passing below params

{
  "duration": "once",
  "metadata": {
    "credit_id": "f3fef2ab-c8a5-442b-964c-2fd4f3156eb6"
  },
  "max_redemptions": "1",
  "name": "Startup_credit",
  "currency": "usd",
  "amount_off": "1000"
}
com.stripe.model.Coupon.create(params)

On invoice.created, I am trying to set discounts from above coupon on the initial invoice by invoking update. Below is the params based to update invoice

{
  "expand": {
    "0": "discounts",
    "1": "total_discount_amounts.discount",
    "2": "lines.data.tax_amounts.tax_rate",
    "3": "lines.data.price.product"
  },
  "discounts": {
    "0": {
      "coupon": "3j4TRKK2"
    },
    "1": {
      "coupon": "XLw6c1Jv"
    }
  }
}
// code to update stripe invoice
final ArrayList<Object> expandList = new ArrayList<>();
expandList.add("discounts");
expandList.add("total_discount_amounts.discount");
expandList.add("lines.data.tax_amounts.tax_rate");
expandList.add("lines.data.price.product");
params.put("expand", expandList);
return invoice.update(params);