Fix (?) issues related with concurrency

Core/Data/CoreContext.cs

@@ -1,28 +1,19 @@
-using System.Threading.Tasks;
+using Kruzya.TelegramBot.Core.EF;
 using Microsoft.EntityFrameworkCore;
 
 namespace Kruzya.TelegramBot.Core.Data
 {
-    public class CoreContext : DbContext
+    public class CoreContext : AutoSaveDbContext
     {
         /// <summary>
         /// The all known users.
         /// </summary>
         public DbSet<BotUser> Users { get; set; }
-        
-        public DbSet<BotUserValue> UserValues { get; set; }
 
-        public override void Dispose()
-        {
-            SaveChanges();
-            base.Dispose();
-        }
-        
-        public override ValueTask DisposeAsync()
-        {
-            SaveChanges(); 
-            return base.DisposeAsync();
-        }
+        /// <summary>
+        /// The all knows user options and values.
+        /// </summary>
+        public DbSet<BotUserValue> UserValues { get; set; }
 
         public CoreContext(DbContextOptions<CoreContext> ctx) : base(ctx)
         {