Add serenity's `CommandId` to slash commands created with poise. To reference it in the help menu

[asibahi]

Discord allows everyone to type command snowflakes, as shown here. Serenity's CommandId type is the COMMAND_ID being used here, as far as I can tell.

Currently in poise when registering commands this info is discarded and not stored in the Framework. So poise's Command objects lacks this info, so I cannot have my commands linked from the help menu.

tl;dr : this would be nice if I could do it automatically from the help menu. Even if just as a cmd.format_for_discord() method on poise::Command.