fix: properly implement saveFile method and write test

tests/CreatedWithIdResponse.spec.ts

@@ -0,0 +1,28 @@
+import { expect } from 'chai';
+import { CreatedWithIdResponse } from '../src/models/CreatedWithIdResponse';
+
+describe('CreatedWithIdResponse', function () {
+  it('should be defined', function () {
+    expect(CreatedWithIdResponse).to.not.be.undefined;
+  });
+
+  it('should have a constructor', function () {
+    expect(CreatedWithIdResponse).to.have.property('constructor');
+  });
+
+  it('should have 1 parameters', function () {
+    expect(CreatedWithIdResponse).to.have.lengthOf(1);
+  });
+
+  it('should create a new instance of the CreatedWithIdResponse class', function () {
+    expect(() => new CreatedWithIdResponse(1)).to.not.throw();
+  });
+
+  it('should have a property named id', function () {
+    expect(new CreatedWithIdResponse(1)).to.have.property('id');
+  });
+
+  it('should set the id property to the value passed to the constructor', function () {
+    expect(new CreatedWithIdResponse(1).id).to.equal(1);
+  });
+});