feat(user-sessions): implement GameLobby and user session management with exception handling

knockoutwhistweb/app/model/sessions/PlayerSession.scala

@@ -1,6 +1,5 @@
 package model.sessions
 
-import de.knockoutwhist.player.AbstractPlayer
 import de.knockoutwhist.utils.events.SimpleEvent
 
 import java.util.UUID
@@ -9,7 +8,6 @@ trait PlayerSession {
   
   def id: UUID
   def name: String
-  def player: AbstractPlayer
   def updatePlayer(event: SimpleEvent): Unit
   
 }