[#1] Define SDK structure

TODO: Вынести маппинг модель -> grpc в отдельный слой

Signed-off-by: Ivan Pchelintsev <i.pchelintsev@yadro.com>

sdk/src/FrostFS.SDK.ProtosV2/session/Extension.MetaHeader.cs

@@ -0,0 +1,18 @@
+namespace FrostFS.Session
+{
+    public partial class RequestMetaHeader : IMetaHeader
+    {
+        public IMetaHeader GetOrigin()
+        {
+            return Origin;
+        }
+    }
+
+    public partial class ResponseMetaHeader : IMetaHeader
+    {
+        public IMetaHeader GetOrigin()
+        {
+            return Origin;
+        }
+    }
+}