curl --request GET \
  --url https://toncenter.com/api/v3/vesting

{
  "address_book": {},
  "vesting_contracts": [
    {
      "address": "<string>",
      "cliff_duration": 123,
      "owner_address": "<string>",
      "sender_address": "<string>",
      "start_time": 123,
      "total_amount": "<string>",
      "total_duration": 123,
      "unlock_period": 123,
      "whitelist": [
        "<string>"
      ]
    }
  ]
}