Filters don't apply to reverse foreign keys.

[William-Wildridge]

The get_nested_field() function by @pablodiazgtierrez is a really nice addition to this library, but doesn't seem to work for reverse relationships.

I have the same use case as Pablo (needing to filter by company in a multitennant SAAS). However in my use case the object relationship direction of the object is a reverse one, (Example Model below).

I'm using this line in get_extra_filter_kwargs:

def get_extra_filter_kwargs(request, *args, **kwargs):
            return {
                'companies__company': request.user.memberships.first().company,
            }

Similar to Pablo's original issue, for requests to /Users?filter=userName+eq+"example_username" the result is blank, but /Users/1 and Users?attributes=userName do work correctly, and apply the company restrictions as expected.

I think I've diagnosed that the hasattr() line (shown below) that was added in this merge is causing this the filtering to stop prematurely.

            if not hasattr(obj, field_name):
                return None

Example Model

class UserInCompany(models.Model):
        company = models.ForeignKey(Company, related_name = 'company_members', on_delete=models.CASCADE,  null=True, blank=True)
	user = models.ForeignKey(User, on_delete=models.CASCADE, related_name = 'memberships', null=True, blank=True)

class Company(models.Model):
        company_name = models.CharField(max_length=200, null=True, blank=True)

Originally posted by @William-Wildridge in #48 (comment)