Fix add slots in synchro device. (#49)

EpinelPS/LobbyServer/Character/SynchroAddSlotByItem.cs

@@ -0,0 +1,39 @@
+using EpinelPS.Database;
+using EpinelPS.Utils;
+
+namespace EpinelPS.LobbyServer.Character
+{
+    [PacketPath("/character/synchrodevice/addslotbyitem")]
+    public class SynchroAddSlotByItem : LobbyMsgHandler
+    {
+        protected override async Task HandleAsync()
+        {
+            // Broken protocol so we didn't validate request data.
+            // May fix later.
+            ReqSynchroAddSlot req = await ReadData<ReqSynchroAddSlot>();
+            
+            User user = GetUser();
+            ResSynchroAddSlot response = new();
+
+            NetSynchroSlot newSlot = new()
+            {
+                Csn = 0,
+                Slot = user.SynchroSlots.Last().Slot + 1, // any upper bound?
+                AvailableRegisterAt = 0
+            };
+
+            user.SynchroSlots.Add(new SynchroSlot()
+            {
+                Slot = newSlot.Slot,
+                CharacterSerialNumber = newSlot.Csn,
+                AvailableAt = newSlot.AvailableRegisterAt
+            });
+
+            response.Slot = newSlot;
+
+            JsonDb.Save();
+
+            await WriteDataAsync(response);
+        }
+    }
+}