Add rating date tootip, and avoid registering twice a player

api-webapp/src/main/kotlin/org/jeudego/pairgoth/api/PlayerHandler.kt

@@ -23,6 +23,9 @@ object PlayerHandler: PairgothApiHandler {
         val tournament = getTournament(request)
         val payload = getObjectPayload(request)
         val player = Player.fromJson(payload)
+        player.externalIds.forEach { dbId, pId ->
+            if (tournament.hasPlayer(dbId, pId)) badRequest("player already registered")
+        }
         tournament.players[player.id] = player
         tournament.dispatchEvent(PlayerAdded, request, player.toJson())
         return Json.Object("success" to true, "id" to player.id)

api-webapp/src/main/kotlin/org/jeudego/pairgoth/model/Tournament.kt

@@ -119,6 +119,7 @@ sealed class Tournament <P: Pairable>(
     }
 
     fun pairedPlayers() = games.flatMap { it.values }.flatMap { listOf(it.black, it.white) }.toSet()
+    fun hasPlayer(dbId: DatabaseId, pId: String) = players.values.filter { player -> pId == player.externalIds[dbId] }.isNotEmpty()
 }
 
 // standard tournament of individuals