(Add) Implement IRC keys and external auth endpoint for System Bots

[zze0s]

This PR adds IRC Keys for users (like rss/pass/api keys) and an endpoint /api/irc/authenticate which allow System Bot users to do requests from for example an IRC bot for inviting users to a channel.

Not sure if this is wanted or not. I'll maintain this feature and support if needed.

Multiple UNIT3D sites have implemented some variant of this in their codebases but something official might be a good idea.

It could be changed to something more generic such as External Keys or similar, if it's too limited being tied to IRC.

I tried to follow how API/Pass/RSS keys are setup, but I am missing something because it doesn't actually find any keys in IrckeyAuthController.php#39.

PR for the IRC bot changes https://codeberg.org/ze0s/UNIT3D-Announcer/pulls/2

Related #4356

[Roardom]

but I am missing something because it doesn't actually find any keys

It looks like your code is halfway relying on using the latest non-deleted irckey from the irckey table, but at other times you're using a non-existent column on the users table.