curl --request PATCH \
  --url https://api.cashful.africa/api/canary/customers/{id} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "metadata": {
    "orderId": "12345",
    "customField": "value"
  }
}
'

{
  "id": "customer_789",
  "merchantId": "merchant_456",
  "phoneNumber": "+27821234567",
  "email": "john.doe@example.com",
  "name": "John Doe",
  "metadata": {
    "source": "web",
    "referralCode": "FRIEND123"
  },
  "createdAt": "2025-01-15T10:30:00.000Z",
  "updatedAt": "2025-01-15T10:30:00.000Z"
}