Notification on number of players below the required minimum (of 3)

[ivellios]

Once player leaves the game and the number of players drop below 3 (which is minimum for AL legal game session), we will send notification about the event to DM and other players.

The notification body should be:

A player has signed out from the game session and now there's not enough players (minimum of 3) for the game to be AL legal. If no other player joins the game session before the session date it will be cancelled.

Also it should include the basic info on the impacted game session.