today we have two fields:

Site Url is a domain, and gotrue will allow redirects on any path that is on that primary domain

Additional Urls are exact Urls (including path, query param etc.) that do not have to be on the primary domain. The primary use case for these was mobile deep links that look like: com.mydomain.sub://customscheme, hence why they have to be exact, because they are difficult to verify securely

Now it appears that a new use case has developed for these Additional URLs: multiple environments

people may wish to use the same backend for multiple environments and therefore require arbitrary paths on a secondary domain

options here seem to be:

• figure out a way to securely parse Additional URLs - supporting reverse URLs with custom schemes
• introduce "Additional Site URLs" that are restricted to standard scheme://sub.domain.com
• make use of gotrue's multi-tenancy (you can dynamically load configs in and out, but thus far we haven't dug into this capability)
• other?