Expand registration status indication

[kjhoerr]

Mastodon 2.1.0 added the ability to "invite" people to register for instances. This is a great tool for instances that have had issues with abuse because they can filter registrants before they have a chance to cause any issues. While this is great for protecting the server itself it hurts publicity, because they appear closed on instances.social. joinmastodon.org won't even show closed registration instances. I could be wrong, but it seems to me that the closed/open description of an instance is to identify instances that are personal, organizational, or simply closed to new users. This misidentifies all of the instances that have closed registration for the purposes of filtering.

In that case registration isn't completely closed, it simply depends on a filtering process (application-for-invite). Mastodon still doesn't have a built in way to address application-for-invite; most admins use their own methods, like Google Forms. While I would be partial to adding application-for-invites to Mastodon itself, we can work to fix this at a higher level first, at least. That way we can try to help people find the right instances to their fit!

For instances.social, this would depend on expanding the automatically delineated closed/open registration to allow admins to give a better description for what their instance permits. Upon visiting the instance owner page for a given instance, admins could choose a different option to describe their instance as "application-for-invite", and either describe the conditions or leave it to the instance's own description to indicate what sort of applicants are excepted.

I hope that at the very least this can generate some discussion, and we can give instances more opportunities for interfacing with potential users. Thanks!