fix: make domain optional

Ticket: DX-637

Author: Ansh Chaturvedi

packages/openapi-generator/src/ir.ts

@@ -38,7 +38,7 @@ export type Object = {
 
 export type RecordObject = {
   type: 'record';
-  domain: Schema;
+  domain?: Schema;
   codomain: Schema;
 };