title: Is there a way to conditionally validate with class-validator?
body: <p>I'm building a CRUD for users using Nest.js<br>
  I'd like to have the POST and PATCH receive the same DTO but have some fields optional in PATCH but mandatory in POST.<br><br>
  I couldn't find a way to do this other than keep all properties @IsOptional and manually write the validation in the code for POST requests.</p>
  <p>Is there a better way to do it with class-validator ?</p>