Create session

curl --request POST \
  --url https://api.enterprise.sandbox.uphold.com/widgets/payment/sessions \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "flow": "select-for-deposit"
}'

{
  "session": {
    "flow": "select-for-deposit",
    "url": "https://payment.enterprise.uphold.com/",
    "token": "GEbRxBN...edjnXbL"
  }
}