feat: session state token (#3228)

https://jira.unity3d.com/browse/MTT-10043


https://docs.google.com/document/d/1st5PoxRa7rg5JsLW0pKbVAgaqBP1QdUCx2gFlHXEicg/edit?tab=t.0

Adding a SessionStateToken to the ConnectionApproved message and
incrementing the version. This is safe without implementing the feature
as the service does not need to make any assumptions about what the
client does with this information.

## Changelog

- Added: Session State Token into the ConnectionApproved message

## Testing and Documentation

- Tested using E2E tests and existing tests

## Related PR

Unity-Technologies/mps-common-multiplayer-backend#976

Author: DSchroer

com.unity.netcode.gameobjects/Runtime/Configuration/SessionConfig.cs

@@ -8,9 +8,10 @@ internal class SessionConfig
         public const uint NoFeatureCompatibility = 0;
         public const uint BypassFeatureCompatible = 1;
         public const uint ServerDistributionCompatible = 2;
+        public const uint SessionStateToken = 3;
 
         // The most current session version (!!!!set this when you increment!!!!!)
-        public static uint PackageSessionVersion => ServerDistributionCompatible;
+        public static uint PackageSessionVersion => SessionStateToken;
 
         internal uint SessionVersion;
 

com.unity.netcode.gameobjects/Runtime/Messaging/Messages/ConnectionApprovedMessage.cs

@@ -9,6 +9,7 @@ internal struct ServiceConfig : INetworkSerializable
         public bool IsRestoredSession;
         public ulong CurrentSessionOwner;
         public bool ServerRedistribution;
+        public ulong SessionStateToken;
 
         public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReaderWriter
         {
@@ -22,6 +23,11 @@ public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReade
                 {
                     serializer.SerializeValue(ref ServerRedistribution);
                 }
+
+                if (SessionVersion >= SessionConfig.SessionStateToken)
+                {
+                    serializer.SerializeValue(ref SessionStateToken);
+                }
             }
             else
             {
@@ -37,6 +43,15 @@ public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReade
                 {
                     ServerRedistribution = false;
                 }
+
+                if (SessionVersion >= SessionConfig.SessionStateToken)
+                {
+                    serializer.SerializeValue(ref SessionStateToken);
+                }
+                else
+                {
+                    SessionStateToken = 0;
+                }
             }
         }
     }