[#24] Client: Implement pool part1

first iteration - base classes and methods

Signed-off-by: Pavel Gross <p.gross@yadro.com>

src/FrostFS.SDK.ClientV2/Exceptions/SessionNotFoundException.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace FrostFS.SDK.ClientV2;
+
+public class SessionNotFoundException : FrostFsException
+{
+    public SessionNotFoundException()
+    {
+    }
+
+    public SessionNotFoundException(string message) : base(message)
+    {
+    }
+
+    public SessionNotFoundException(string message, Exception innerException) : base(message, innerException)
+    {
+    }
+}