[#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.ClientV2/Services/Session.cs

@@ -0,0 +1,47 @@
+using FrostFS.Refs;
+using FrostFS.SDK.ModelsV2;
+using FrostFS.Session;
+using Google.Protobuf;
+
+namespace FrostFS.SDK.ClientV2;
+
+public partial class Client
+{
+    public async Task<SessionToken> CreateSessionAsync(ulong expiration)
+    {
+        var request = new CreateRequest
+        {
+            Body = new CreateRequest.Types.Body
+            {
+                OwnerId = new OwnerID
+                {
+                    Value = ByteString.CopyFrom(OwnerId.FromKey(_key).ToHash())
+                },
+                Expiration = expiration,
+            }
+        };
+        request.AddMetaHeader();
+        request.Sign(_key);
+        return await CreateSession(request);
+    }
+
+    public async Task<SessionToken> CreateSession(CreateRequest request)
+    {
+        var resp = await _sessionServiceClient.CreateAsync(request);
+        return new SessionToken
+        {
+            Body = new SessionToken.Types.Body
+            {
+                Id = resp.Body.Id,
+                SessionKey = resp.Body.SessionKey,
+                OwnerId = request.Body.OwnerId,
+                Lifetime = new SessionToken.Types.Body.Types.TokenLifetime
+                {
+                    Exp = request.Body.Expiration,
+                    Iat = resp.MetaHeader.Epoch,
+                    Nbf = resp.MetaHeader.Epoch,
+                }
+            }
+        };
+    }
+}