Broadcast: Notify about players without assigned FIDE ID

[AAArmstark]

Players in broadcasts can be assigned a FIDE ID, which automatically replaces their name, rating and title, adds a federation flag and lists the (official) broadcasts on their FIDE player profile page (https://lichess.org/fide/1503014/Carlsen_Magnus), if the ID exists in our FIDE player database.

As the Lichess Broadcast Team would like to use this feature whenever possible (whenever a player is part of our FIDE player database), we could need an automated way to notify the Broadcast Team about players in broadcasts who haven't been assigned a FIDE ID.

Ideally a notification would be sent to zulip, containing the link to the broadcast round or the games with the players who don't have a FIDE ID. This could for example be done at the start of the round, when the first move comes in, but maybe there's a better way.

Currently the Broadcast Team has to manually check every round in every broadcast for players who haven't been assigned a FIDE ID, which is not realistically possible.