Adds custom metadata to the request. Metadata fields key-value pairs of type string.

Field names that start with $ are reserved for special use.

The following field names are used for Working With Custom Identifiers:

$email
$internalId
$phoneNumber

In addition, you can override a specific integration's identifier by setting a field called '${integrationType}. This will work regardless if the integration was designed to use email or any other identifier.

Example: To set the userId 123-456 for use with Google BigQuery integration, set the following field name:

"customFields": {
  "$googlebq": "123-456"
}

If you set a value for one or more of these fields, they will be used by integrations when fulfilling requests.

Setting an empty value

Marking an identifier as empty (i.e. value does not exist) can be done by setting "x-none" as the value.