curl --request POST \
  --url https://api.example.com/api/v1/workspaces/{workspace_id}/billing/payment-methods \
  --header 'Content-Type: application/json' \
  --header 'X-API-Key: <api-key>' \
  --data '
{
  "payment_method_id": "<string>",
  "set_as_default": true
}
'

{
  "is_default": true,
  "payment_method": {
    "brand": "<string>",
    "exp_month": 123,
    "exp_year": 123,
    "last4": "<string>"
  }
}