fix: resolve reference not working for federation 2

Author: greguintow

packages/graphql/lib/federation/graphql-federation.factory.ts

@@ -243,7 +243,10 @@ export class GraphQLFederationFactory {
             ...autoGeneratedObjectType.astNode,
           };
         }
-        type.extensions = autoGeneratedObjectType.extensions;
+        type.extensions = {
+          ...type.extensions,
+          ...autoGeneratedObjectType.extensions,
+        };
         return type;
       } else if (isScalarType(type) && type.name === 'DateTime') {
         const autoGeneratedScalar = autoGeneratedSchema.getType(