Add DbConnection argument to OnConnect (#138)

## Description of Changes
*Describe what has been changed, any new features or bug fixes*

## API

 - [ ] This is an API breaking change to the SDK

*If the API is breaking, please state below what will break*


## Requires SpacetimeDB PRs
*List any PRs here that are required for this SDK change to work*

Author: lcodes

sdks/csharp/examples~/quickstart/client/Program.cs

@@ -26,8 +26,7 @@ void Main()
         .WithUri(HOST)
         .WithModuleName(DBNAME)
         //.WithCredentials((null, AuthToken.Token))
-        // TODO: change this to just `(OnConnect)` when signature is fixed in #131.
-        .OnConnect((identity, authToken) => OnConnect(conn!, identity, authToken))
+        .OnConnect(OnConnect)
         .OnConnectError(OnConnectError)
         .OnDisconnect(OnDisconnect)
         .Build();

sdks/csharp/src/SpacetimeDBClient.cs

@@ -58,9 +58,9 @@ public DbConnectionBuilder<DbConnection, Reducer> WithCredentials(in (Identity i
             return this;
         }
 
-        public DbConnectionBuilder<DbConnection, Reducer> OnConnect(Action<Identity, string> cb)
+        public DbConnectionBuilder<DbConnection, Reducer> OnConnect(Action<DbConnection, Identity, string> cb)
         {
-            conn.onConnect += cb;
+            conn.onConnect += (identity, token) => cb.Invoke(conn, identity, token);
             return this;
         }