Make certain Storefront configurations configurable in the Admin app

[ArchitectedDev]

Storefronts are currently being driven by individual API clients, which we could leverage the API Client xp to drive storefront configurations, such as supported languages.

@crhistianramirez has also considered something more dynamic like mapping a domain to an API client. That requires a bit more set up the first time around but has some powerful implications. For example, if someone has a wildcard domain they could theoretically pop up new buyers pretty much at will without any kind of deployment process.