Identifier type that the event's content_ids field should be matched against for items in this catalog. For example, 'gtin' means content_ids values are Global Trade Item Numbers, 'sku' means retailer SKUs. Omit when using a custom identifier scheme not listed in the enum.
Identifier type that the event's content_ids field should be matched against for items in this catalog. For example, 'gtin' means content_ids values are Global Trade Item Numbers, 'sku' means retailer SKUs. Omit when using a custom identifier scheme not listed in the enum.