fix: begin writing Lists integration tests. fix: list item response model's id value should be of type string so modified the created with id response model that it extends so that the id property is generically typed and type can be passed in.

src/models/SaveRecordResponse.ts

@@ -1,6 +1,6 @@
 import { CreatedWithIdResponse } from './CreatedWithIdResponse';
 
-export class SaveRecordResponse extends CreatedWithIdResponse {
+export class SaveRecordResponse extends CreatedWithIdResponse<number> {
   public warnings: string[];
 
   constructor(id: number, warnings: string[] = []) {