Make values of MentionableSelect distinguishable

[NVedsted]

I am using mentionable select menus in a project where I ran into GenericIds being returned when receiving data. It would be nice to receive a union type of roles and users such that they can be distinguished. My current solution to distinguishing is simply to first see if the ID is cached as a user then as a role on the guild if it occurred in a guild.

Discord already sends resolved values during this interaction so there is a better approach than looking into the caches. By simply adding something like this, it becomes much easier to work with:

pub struct ComponentInteractionData {
    // ...
    pub resolved: Option<CommandDataResolved>,
}

Ideally, having the values of the kind contain some union type that can be distinguished would be nice. I.e., the variant was something like this:

pub enum ComponentInteractionDataKind {
  // ...
  MentionableSelect { values: Vec<UserOrRoleId> },
  // ...
}

Or at the very least have a method that can spit something like that out.

I am willing to help with implementing this as well, but I will certainly need input on how you want it to be approached. :)