[#13] Client: Use code analyzers

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

src/FrostFS.SDK.ClientV2/Mappers/Netmap/PlacementPolicy.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 
 using FrostFS.Netmap;
@@ -6,26 +7,13 @@ namespace FrostFS.SDK.ClientV2;
 
 public static class PlacementPolicyMapper
 {
-    public static PlacementPolicy ToMessage(this FrostFsPlacementPolicy placementPolicy)
-    {
-        var pp = new PlacementPolicy
-        {
-            Filters = { },
-            Selectors = { },
-            Replicas = { },
-            Unique = placementPolicy.Unique
-        };
-
-        foreach (var replica in placementPolicy.Replicas)
-        {
-            pp.Replicas.Add(replica.ToMessage());
-        }
-
-        return pp;
-    }
-
     public static FrostFsPlacementPolicy ToModel(this PlacementPolicy placementPolicy)
     {
+        if (placementPolicy is null)
+        {
+            throw new ArgumentNullException(nameof(placementPolicy));
+        }
+
         return new FrostFsPlacementPolicy(
             placementPolicy.Unique,
             placementPolicy.Replicas.Select(replica => replica.ToModel()).ToArray()