How do I apply a discount in a subscription billing?

[pjha]

I am using the billing API example and would like to know how to add a discount in terms of both percentage and amount. Thanks!

link: https://shopify.dev/docs/api/shopify-app-remix/v2/apis/billing#require-requesting-billing-right-away

const shopify = shopifyApp({
// ...etc
billing: {
[MONTHLY_PLAN]: {
amount: 5,
currencyCode: 'USD',
interval: BillingInterval.Every30Days,
},
[ANNUAL_PLAN]: {
amount: 50,
currencyCode: 'USD',
interval: BillingInterval.Annual,
},
}
});