title: Django: Show reverse ForeignKey lookup on admin page, as read-only list?
body: <p>I'd like to show a reverse ForeignKey lookup on a Django admin page, and make it read-only, as a lightweight list of strings. </p>
  
  <p>The standard way to do this seems to be with an inline admin field, but I don't want it to be editable, so I wonder if there's a lighter-weight way to do it. </p>
  
  <p>These are my fields: </p>
  
  <pre><code>class Book: 
    title = models.TextField(blank=True)
    author = models.ForeignKey(Author, on_delete=models.PROTECT)
  
  class Author: 
    name = models.TextField(blank=True)
  </code></pre>
  
  <p>On the admin change/delete page for an author, I'd like to show a read-only list of their books.</p>
  
  <p>I can do this with an <code>admin.StackedInline</code>, but it's quite cumbersome to make it read-only: </p>
  
  <pre><code>class BooksInline(admin.StackedInline):
    model = Book
    fields = ('title',)
    readonly_fields = ('title',)
  
    def has_add_permission(request, obj):
      return False
  
    def has_delete_permission(request, obj, self):
      return False
  </code></pre>
  
  <p>And the resulting list takes up a lot of space on the page, because the design expects it all to be editable. </p>
  
  <p>Is there a simpler way to make a read-only list?</p>