[feature/admin] Drop messages from other instances based on a filter/regex

[f0x52]

Similar to users filtering messages it would be nice for admins to be able to set global filters too, either adding a CW or dropping toots completely based on instance/user/toot content

[technomancy]

I have a very rough proof of concept of this here: technomancy@a690b18

It allows you to write plugins in Lua or Fennel which get loaded at boot and can add CWs or change the contents of statuses.

It's extremely rough and hacky (I've basically never used golang before) but it's a pretty small change if you want to try running a fork instead of mainline gts. I'm not sure it makes sense for mainline gts because it brings in a rather large dependency.

[NyaaaWhatsUpDoc]

i currently have work funded to add something along these lines which i plan to work on in the next few months :)

the actual work is to be able to modify incoming messages specifically only to add CWs based on filtering, but as part of it i will be making it modularisable / pluggable so adding filtering to drop messages really wouldn't be much on top of it at all