title: Angular Typescript: Swagger CodeGen Generator making all class properties Nullable
body: <p>We are auto generating proxies with SwaggerCodeGen <a href="https://swagger.io/" rel="noreferrer">https://swagger.io/</a> .</p>
  <p>This will reduce manually typing in hundreds of classes. We noticed all model class properties are Nullable ? in SwaggerCodeGen.</p>
  <p>When they wrote this, doesn't it break the interface contract when some members as required?
  What is the reason SwaggerCodeGen did this? In our same C# corresponding class, they are not nullable.</p>
  <pre><code>export interface Product{ 
      productId?: number;
      productName?: string;
      productType?: number;
      manufacturer?: string;
      inventory?: number;
  </code></pre>
  <p>Currently converting C# classes to Angular Typescript 10.</p>
  <p><a href="https://i.stack.imgur.com/EndNo.png" rel="noreferrer"><img src="https://i.stack.imgur.com/EndNo.png" alt="enter image description here" /></a></p>
  <p><strong>Another topic:</strong></p>
  <p>Similarly in NSwag Studio,</p>
  <p>They are doing this with Union Types undefined, instead of nullable. Is this the same thing as Swagger CodeGen,</p>
  <pre><code>export interface Product {
      productId: number | undefined;
      productName?: string | undefined;
      productType?: number | undefined;
      manufacturer?: string | undefined;
      inventory?: number | undefined;
  </code></pre>