Members of the BOT usergroup shouldn't be able to be assigned guest difficulties

[Nivalyx]

Self-explanatory I guess.

Related to the recent incident on this map, where the mapset host tried to set the ownership of his map to bot accounts such as "BanchoBot" and "Nomination Assessment Team" :

[notbakaneko]

I knew I forgot something 👀

[nanaya]

what's the impact though?

[cl8n]

I don't think this needs to be treated any differently than the general case of abusing owner change feature

[peppy]

I'd still block it just because it never makes sense for a bot to be an owner.

[notbakaneko]

Related since they're currently using the same lookup, what about chat announcements and supporter tag gifts?