title: Django model field for file system directory path
body: <p>In the Django model field types reference I could not find a field for a file system directory path. With <a href="https://docs.djangoproject.com/en/2.2/howto/custom-model-fields/" rel="nofollow noreferrer">custom model fields</a> it's possible to implement this. What should be considered w.r.t. validation? Can I extend Django's builtin model field types with a package?</p>