django-filter custom field extensions do not allow for serializer fields

[realsuayip]

Describe the bug

When specifying custom annotations for filters.Filter classes, only the basic types and raw openapi definitions are allowed:

drf-spectacular/drf_spectacular/contrib/django_filters.py

Lines 96 to 100 in d57ff26

	if is_basic_type(annotation):
	schema = build_basic_type(annotation)
	else:
	# allow injecting raw schema via @extend_schema_field decorator
	schema = annotation.copy()

To Reproduce

from django_filters import rest_framework as filters

@extend_schema_field(serializers.CharField())
class CustomFilter(filters.Filter):
    field_class = django.forms.CharField

and use following filter in a view:

from django_filters import rest_framework as filters

class SomeFilter(filters.FilterSet):
    something = CustomFilter(required=True)

File "/usr/local/lib/python3.11/site-packages/drf_spectacular/contrib/django_filters.py", line 63, in get_schema_operation_parameters
result += self.resolve_filter_field(
          ^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/local/lib/python3.11/site-packages/drf_spectacular/contrib/django_filters.py", line 100, in resolve_filter_field
schema = annotation.copy()
         ^^^^^^^^^^^^^^^
AttributeError: 'CharField' object has no attribute 'copy'

Expected behavior

I should be able to specify serializer fields in filter annotations.