Define Digital Asset Links on all sites served by the project

[toolness]

One of the current downsides of our multi-website strategy (having the same login for norent.org, evictionfreeny.org, and app.justfix.nyc) is that the user has no easy way of sharing their actual login state, or even credentials (via password manager) across the sites.

It looks like there is a standard called Digital Asset Links that allows websites to host a file at /.well-known/assetlinks.json that tells a browser about what other domains it can share the user's credentials with. It's a very new standard and is only supported by the very latest versions of Chrome (I'm not sure if other browsers even support it) and I'm not sure exactly how it works in practice, but it might be worth looking into.