title: Trouble setting up nested associations
body: <p>I'm working a document management application that allows suppliers to collect documents from doctors and I'm really struggling with the associations.  I'm hoping someone can review my association structure, as I'm getting errors and not sure I'm on the right track.</p>
  
  <p>Basically, a patient can have several different documents - say one for a hospital bed and one for oxygen in this case.  A supplier would have a single patient, who has several documents.  I've built seperate scaffolds so that I can roll up all the documents into a single page per patient.  </p>
  
  <pre><code>                                :supplier
                                      |
                              has_many :patients
                                      |
                                  :patients
                                      |
                              has_many :documents
                              belongs_to :supplier
                                      |
                                  :documents
                      belongs_to :supplier, through: :patients
              ________________________|____________________
              |                                           |
          :oxygen                                 :hosptialbeds
  belongs_to :patient, through: :documents    belongs_to :patient,through: documents
  </code></pre>
  
  <p>I'm sure I'm not making an needed association here, but I'm too new to know better...  If there's a better way to arrive at this, I would love to hear it.</p>
  
  <p>Rails 4.0
  Postgresql DB</p>