Implement auto countdown timers

Change to using TimeSpan

osu.Game/Online/Multiplayer/MultiplayerClient.cs

@@ -239,7 +239,9 @@ namespace osu.Game.Online.Multiplayer
         /// <param name="password">The new password, if any.</param>
         /// <param name="matchType">The type of the match, if any.</param>
         /// <param name="queueMode">The new queue mode, if any.</param>
-        public Task ChangeSettings(Optional<string> name = default, Optional<string> password = default, Optional<MatchType> matchType = default, Optional<QueueMode> queueMode = default)
+        /// <param name="autoStartDuration">The new auto-start countdown duration, if any.</param>
+        public Task ChangeSettings(Optional<string> name = default, Optional<string> password = default, Optional<MatchType> matchType = default, Optional<QueueMode> queueMode = default,
+                                   Optional<TimeSpan> autoStartDuration = default)
         {
             if (Room == null)
                 throw new InvalidOperationException("Must be joined to a match to change settings.");
@@ -250,6 +252,7 @@ namespace osu.Game.Online.Multiplayer
                 Password = password.GetOr(Room.Settings.Password),
                 MatchType = matchType.GetOr(Room.Settings.MatchType),
                 QueueMode = queueMode.GetOr(Room.Settings.QueueMode),
+                AutoStartDuration = autoStartDuration.GetOr(Room.Settings.AutoStartDuration),
             });
         }
 

osu.Game/Online/Multiplayer/MultiplayerRoomSettings.cs

@@ -28,6 +28,9 @@ namespace osu.Game.Online.Multiplayer
         [Key(4)]
         public QueueMode QueueMode { get; set; } = QueueMode.HostOnly;
 
+        [Key(5)]
+        public TimeSpan AutoStartDuration { get; set; }
+
         public bool Equals(MultiplayerRoomSettings? other)
         {
             if (ReferenceEquals(this, other)) return true;
@@ -37,13 +40,15 @@ namespace osu.Game.Online.Multiplayer
                    && Name.Equals(other.Name, StringComparison.Ordinal)
                    && PlaylistItemId == other.PlaylistItemId
                    && MatchType == other.MatchType
-                   && QueueMode == other.QueueMode;
+                   && QueueMode == other.QueueMode
+                   && AutoStartDuration == other.AutoStartDuration;
         }
 
         public override string ToString() => $"Name:{Name}"
                                              + $" Password:{(string.IsNullOrEmpty(Password) ? "no" : "yes")}"
                                              + $" Type:{MatchType}"
                                              + $" Item:{PlaylistItemId}"
-                                             + $" Queue:{QueueMode}";
+                                             + $" Queue:{QueueMode}"
+                                             + $" Start:{AutoStartDuration}";
     }
 }

osu.Game/Online/Rooms/Room.cs

@@ -92,6 +92,16 @@ namespace osu.Game.Online.Rooms
             set => QueueMode.Value = value;
         }
 
+        [Cached]
+        public readonly Bindable<TimeSpan> AutoStartDuration = new Bindable<TimeSpan>();
+
+        [JsonProperty("start_duration")]
+        private ushort autoStartDuration
+        {
+            get => (ushort)AutoStartDuration.Value.TotalSeconds;
+            set => AutoStartDuration.Value = TimeSpan.FromSeconds(value);
+        }
+
         [Cached]
         public readonly Bindable<int?> MaxParticipants = new Bindable<int?>();
 
@@ -172,6 +182,7 @@ namespace osu.Game.Online.Rooms
             EndDate.Value = other.EndDate.Value;
             UserScore.Value = other.UserScore.Value;
             QueueMode.Value = other.QueueMode.Value;
+            AutoStartDuration.Value = other.AutoStartDuration.Value;
             DifficultyRange.Value = other.DifficultyRange.Value;
             PlaylistItemStats.Value = other.PlaylistItemStats.Value;
             CurrentPlaylistItem.Value = other.CurrentPlaylistItem.Value;