curl --request GET \
  --url http://127.0.0.1:8080/v1/c/entitlement/{customer_id}/billing \
  --header 'wb-key: <api-key>'

{
  "contract": {
    "contract_id": "Cust_c40bea18-c0c9-44b1-bd0c-43f5283e1670",
    "status": "active"
  },
  "customer": {
    "status": "active"
  },
  "payment": {
    "next_payment_due": "2023-11-07T05:31:56Z",
    "payment_provider": "stripe",
    "unpaid_invoices_info": [
      {
        "currency": "usd",
        "payment_threshold": "<string>",
        "total_unpaid": "<string>",
        "unpaid_invoices": [
          {
            "amount": "<string>",
            "due_date": "2023-11-07T05:31:56Z",
            "id": "Cust_c40bea18-c0c9-44b1-bd0c-43f5283e1670",
            "status": "pending_validation"
          }
        ]
      }
    ],
    "wallet_balance": "<string>",
    "wallet_balances": [
      {
        "balance": "<string>",
        "currency": "usd",
        "customer_id": "Cust_c40bea18-c0c9-44b1-bd0c-43f5283e1670",
        "id": "Cust_c40bea18-c0c9-44b1-bd0c-43f5283e1670",
        "wb_customer_id": "Cust_c40bea18-c0c9-44b1-bd0c-43f5283e1670"
      }
    ]
  }
}