discord: option to add/remove role on enable/disable/deletion

in Settings > Discord, shown when a role is selected in "Apply Role".
The discord housekeeping daemon should pick up users deleted outide of
jfa-go too, so users who delete their own accounts should have their
roles removed (periodically).

housekeeping-d.go

@@ -36,6 +36,8 @@ func (app *appContext) clearDiscord() {
 		// Make sure the user doesn't exist, and no other error has occured
 		switch err.(type) {
 		case mediabrowser.ErrUserNotFound:
+			// Remove role in case their account was deleted oustide of jfa-go
+			app.discord.RemoveRole(discordUser.MethodID().(string))
 			app.storage.DeleteDiscordKey(discordUser.JellyfinID)
 		default:
 			continue