Test quilt_rails in public apps

[GoodForOneFare]

Overview

Most quilt_rails apps use a Shopify gem that sends users through an oauth flow before they see any site content. This is great for security but:

• It means that quilt_rails apps are guaranteed to have an existing session
• quilt_rails may have unknown assumptions about sessions baked into itself
• We need to find and 🔥 any of these assumptions for this to be usable in public apps

It's possible that everything Just Works, though¯\(ツ)/¯

[cartogram]

Created https://github.com/Shopify/hydrox to verify this. It seems to work well at https://hydrox.shopifycloud.com/

[GoodForOneFare]

Renamed this so that it can be closed :p Fixing first request is a separate issue: #1077