Is there a way to set an allow_domain function per server?

I was just writing up a function to query a database for wether a particular domain is allowed to have an SSL cert issued and realised that I have a couple of other `server` definitions on this server with specific domains in addition to my catch-all server and that these names would have to be checked also.

This won't really be a problem as I can just add a regex check against a list before I go to query the database, but I wondered if it's possible to override the `allow_domain` function per server? I'm new to lua so that's probably where my understanding is falling down. It looks like a function on an object: `auto_ssl`, so I assume there is only room for one function?

Start by reviewing this issue's discussion and locating the existing allow_domain entry point in the project. Determine whether per-server domain checks are supported or require a design decision; done means the intended per-server behavior is agreed and documented or implemented with appropriate verification.

Written by the indexing model from the issue text.