[#28] Client: Apply code optimizations

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

src/FrostFS.SDK.Client/Services/AccountingServiceProvider.cs

@@ -24,12 +24,12 @@ internal sealed class AccountingServiceProvider : ContextAccessor
         {
             Body = new()
             {
-                OwnerId = ctx.OwnerId!.OwnerID
+                OwnerId = ClientContext.Owner.OwnerID
             }
         };
 
         request.AddMetaHeader(args.XHeaders);
-        request.Sign(ctx.Key!);
+        request.Sign(ClientContext.Key.ECDsaKey);
 
         var response = await _accountingServiceClient!.BalanceAsync(request, null, ctx.Deadline, ctx.CancellationToken);