Setting these defaults in __init__ would be better, as we're trying to avoid accessing settings until runtime.

Some subtleties around how best to do that, as we'd still want to preserve any value that has been set as a class attribute tho (eg user has a custom relational field, where they've overridden this value)

Might need to be something like:

Don't include these attribute on the class unless overridden, then in __init__, do something like...

if `html_cutoff` in kwargs:
    self.html_cutoff = kwargs.pop('html_cutoff')
elif not hasattr(self, 'html_cutoff`):
    # Use default from settings, unless already set as a class attribute.
    self.html_cutoff = int(api_settings.HTML_SELECT_CUTOFF)