Subclassed PrimaryKeyRelatedField.get_queryset alongside with Serializer fails generating schema

[SafaAlfulaij]

Describe the bug
Using a subclassed serializers.PrimaryKeyRelatedField with get_queryset to validate incoming payloads with a Serializer fails generating schema.

To Reproduce

from rest_framework import serializers

from django.contrib.auth.models import User


class UserRelatedField(serializers.PrimaryKeyRelatedField):
    def get_queryset(self):
        return User.objects.all()


class TestSerializer(serializers.Serializer):
    user_ids = UserRelatedField(many=True)

• Error message: 'TestSerializer' object has no attribute 'Meta'
• Error line: https://github.com/SafaAlfulaij/drf-spectacular/blob/02971bd89e25e0a3cda5f94400ab497f20112f7d/drf_spectacular/openapi.py#L717
• Error reason: we are assuming that PrimaryKeyRelatedField are only used in ModelSerializer objects, which defines a Meta sub class. PrimaryKeyRelatedField can be used in normal Serializer instances.

Expected behavior
Schema generates normally respecting get_queryset.

Others
Using queryset directly in the field (instead of subclassing) works normally.
Subclassing with a get_queryset causes the issue.

Possible Solution
Handling get_queryset solves the issue. I failed to update the test cases, hence didn't open a PR:

            elif queryset := field.get_queryset() and isinstance(queryset, (Queryset, Manager)):
                if is_slug:
                    model = queryset.model
                    source = [field.slug_field]
                    model_field = follow_field_source(model, source, default=models.TextField())
                else:
                    model_field = queryset.model._meta.pk

(We do the check to avoid catching read-only cases.)