Page context data returned from checkout provider endpoint. The response structure varies depending on which page was processed:

Page	Response Fields
`CheckoutProviderIndexPage`	Empty object `{}`
`CheckoutProviderSelectionPage`	`checkout_providers[]`, `redirect_url` (remote payment page)
`CheckoutProviderAddressSelectionPage`	`redirect_url` (to continue on provider)
`CheckoutProviderShippingOptionPage`	`shipping_options[]`
`CheckoutProviderAgreementListPage`	`agreements[]`
`CheckoutProviderNotificationPage`	`return_url`, `merchant_customer_id`, `merchant_customer_date_joined`, `merchant_customer_akifast_date_joined`

All fields are optional since different pages return different subsets.