title: Django admin - giving users access to specific objects/fields?
body: <p>I need to make an "owners" login for the admin. Say we have this model structure:</p>
  
  <pre><code>class Product(models.Model):
      owner = models.ManyToManyField(User)
      name = models.CharField(max_length=255)
      description = models.CharField(max_length=255)
      photos = models.ManyToManyField(Photo, through='ProductPhoto')
  
  
  class Photo(models.Model):
      order = models.IntegerField()
      image = models.ImageField(upload_to='photos')
      alt = models.CharField(max_length=255)
  
  
  class ProductPhoto(models.Model):
      photo = models.ForeignKey(Photo)
      product = models.ForeignKey(Product)
  </code></pre>
  
  <p>We have a group called <code>Owners</code> that some users are part of. The <code>ProductPhoto</code> is a <code>TabularInline</code> on the <code>Product</code> admin page.</p>
  
  <p>Now, owners need permission to edit</p>
  
  <ol>
  <li><p><strong>(primary goal)</strong> <em>only</em> products where <code>product__in=user.products</code> (so basically, only products owned by them).</p></li>
  <li><p><strong>(secondary goal)</strong> <em>only</em> the <strong>description</strong> and <strong>photos</strong> of products</p></li>
  </ol>
  
  <p>How would I do this with Django's admin/permission system?</p>