title: Django - Combine Approval subclasses with different foreign keys into one class
body: <p>Say I have two models in my Django project.</p>
  
  <pre><code>class Project(models.Model):
      name = models.CharField(max_length=256)
  
  class Forecast(models.Model):
      name = models.CharField(max_length=256)
      project = models.ForeignKey(Project)
  </code></pre>
  
  <p>I want to build an Approval model in a standalone app that allows me to combine the following two approval subclasses:</p>
  
  <pre><code>class ProjectApproval(models.Model):
      approver = models.ForeignKey(User)
      approved_object = models.ForeignKey(Project)
  
  class ForecastApproval(models.Model):
      approver = models.ForeignKey(User)
      approved_object = models.ForeignKey(Forecast)
  </code></pre>
  
  <p>into something more generic like:</p>
  
  <pre><code>class Approval(models.Model):
      user = models.ForeignKey(User)
      approved_object = [whatever I want ... a Project, a Forecast, a Checkbook, a Plan]
  </code></pre>
  
  <p>Is this possible?</p>
  
  <p>Thanks,</p>
  
  <p>Mike</p>