fix: handling of params.mongoose in transaction (#358)

extend params.mongoose with session instead of replacing it

lib/transaction-manager.js

@@ -18,7 +18,7 @@ const beginTransaction = async (context, skipPath = []) => {
         const session = await client.startSession();
         await session.startTransaction();
         context.params.transactionOpen = true;
-        context.params.mongoose = { session };
+        context.params.mongoose = { ...context.params.mongoose, session };
       }
       context.enableTransaction = true; // true if transaction is enabled
     } else {