title: What is the correct HTTP status code to respond to a Create operation on a Resource with a OneToMany
body: <p>I have something of a simple usecase: User has a set of Privileges; when I create the User resource I do not want to also create Privileges; so, if a new User with new Privileges comes from the client, I want to respond with something along the lines of: </p>
  
  <blockquote>
    <p>I cannot create the User Resource because the Privileges it contains
    do not exist.</p>
  </blockquote>
  
  <p>At this point, the client can do a Create on the Privilege first and then add them to the User and create that. </p>
  
  <p>The question is <strong>what Error status code to use</strong> for the HTTP response: </p>
  
  <ul>
  <li>412 - Precondition Failed</li>
  <li>424 - Failed Dependency</li>
  </ul>
  
  <p>I also considered (but do not seem to fit the usecase): </p>
  
  <ul>
  <li>400 - Bad Request</li>
  <li>422 - Unprocessable Entity</li>
  </ul>