title: Creating a tastypie resource with a foreign key without exposing the foreign key as a resource
body: <p>There were a number of questions that looked similar to mine but none of them seemed to cover my particular formulation. Apologies if I missed one that covers this.</p>
  
  <p>I have a tastypie ModelResource that is representing a model with a ForeignKey. I want to be able to create new resources of that type, but I don't want to expose the model of the foreign key to the api.</p>
  
  <p>It would be fine to add a resource for it, but I don't want anything external to the site code to be able to read/write the foreign key. From what I've attempted so far though, tastypie seems to only be able to handle this type of foreign key if the corresponding foreign key model also has a resource that can be created. I just want to be able to create models that reference existing foreign key objects, not allow the creation of new ones.</p>
  
  <p>Is this something that can be done in tastypie? If so, what do I need to do in order to accomplish this? If not, is there some kind of work-around/compromise?</p>