How can I add an apple-app-site-association file to a merchant's shop for IOS DeepLink?

[AurimasA]

Our team is developing an authentication flow to connect user's (from our mobile app) account to a purchase session on a merchant's shop. To do that, we need the user to authenticate himself through our application. In order to open an app, we have generated deep link.

The business and UI logic is served through our theme-app-extension. On the start of the authentication flow we redirect the user to the deep link. Deep Link works fine with android devices. However, IOS devices require apple-app-site-association file to be accessible at the root domain (in this case the shop).

Is there any way to add this file to the merchant's shop?