Initiate offramp

curl --request POST \
  --url https://api.privy.io/v1/users/{user_id}/fiat/offramp \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --header 'privy-app-id: <privy-app-id>' \
  --data '{
  "provider": "bridge-sandbox",
  "amount": "100.00",
  "source": {
    "currency": "usdc",
    "chain": "base",
    "from_address": "0xc24272abc794b973b896715db40a72714a030323"
  },
  "destination": {
    "currency": "usd",
    "payment_rail": "ach_push",
    "external_account_id": "a068d2dd-743a-4011-9b62-8ad33cc7a7be"
  }
}'

{
  "id": "d220bcf7-4ad5-4687-8a61-e51c5875225e",
  "status": "awaiting_funds",
  "deposit_instructions": {
    "amount": "100.0",
    "currency": "usdc",
    "to_address": "0xdeadbeef2usdcbase",
    "from_address": "0xc24272abc794b973b896715db40a72714a030323",
    "chain": "base"
  }
}