curl --request POST \
  --url https://api.withorb.com/v1/customers/external_customer_id/{external_customer_id}/credits/top_ups \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "currency": "<string>",
  "threshold": "<string>",
  "amount": "<string>",
  "per_unit_cost_basis": "<string>",
  "invoice_settings": {
    "auto_collection": true,
    "net_terms": 123,
    "memo": "<string>",
    "require_successful_payment": false
  },
  "expires_after": 123,
  "expires_after_unit": "day",
  "active_from": "2023-11-07T05:31:56Z"
}'

{
  "id": "<string>",
  "currency": "<string>",
  "threshold": "<string>",
  "amount": "<string>",
  "per_unit_cost_basis": "<string>",
  "invoice_settings": {
    "auto_collection": true,
    "net_terms": 123,
    "memo": "<string>",
    "require_successful_payment": false
  },
  "expires_after": 123,
  "expires_after_unit": "day"
}