metafield:
Metafield -
A [custom field](https://shopify.dev/docs/apps/build/custom-data),
including its `namespace` and `key`, that's associated with a Shopify resource
for the purposes of adding and storing additional information.
shopifyFunction:
ShopifyFunction! -
The Shopify Function implementing the payment customization.
title:
String! -
The title of the payment customization.