| Name | Type | Description | Notes |
|---|---|---|---|
| holders | [Customer] | Array of holders to be added to a referral card as referees. You have to send at least one object in the array up to a maximum of 100 objects. You can send either a `source_id` or `id`, or both; however, at least one of them is required. If both are sent, Voucherify checks `id` to upsert that customer's data. | [optional] |
| metadata | Object | A set of custom key/value pairs that you can attach to the redeemable holders sent in the array. The value can be a string, number, boolean, date, datetime, image URL, or object. The metadata must meet the metadata schema for publications. The metadata object stores all custom attributes assigned to the redeemable holder. | [optional] |