ValueError: Cannot use ModelSerializer with Abstract Models when generating schema

[maycuatroi1]

Describe the bug
When accessing /api/schema/ endpoint after migrating from drf-yasg to drf-spectacular, the schema generation fails with a ValueError: Cannot use ModelSerializer with Abstract Models. The error occurs during schema generation when drf-spectacular tries to map serializers.

To Reproduce

# The error happens when drf-spectacular tries to generate schema for viewsets that use abstract models
# Stack trace shows the issue occurs in:
# File "...\drf_spectacular\openapi.py", line 1042, in _map_basic_serializer
#     for field in serializer.fields.values():
# File "...\rest_framework\serializers.py", line 1067, in get_fields
#     raise ValueError("Cannot use ModelSerializer with Abstract Models.")

The error is triggered when accessing:

GET /api/schema/ HTTP/1.1

Expected behavior
The schema should be generated successfully without errors. Abstract models should either be skipped or handled appropriately during schema generation.

Additional context

• Recently migrated from drf-yasg to drf-spectacular
• Multiple warnings about WorkflowServiceAuthentication not having an OpenApiAuthenticationExtension
• Warnings about unable to resolve type hints for several serializer methods
• The full stack trace shows the error originates from DiscussionActivityViewSet and related activity viewsets

Environment:

• drf-spectacular version: [latest from migration]
• Django version: [from traceback appears to be recent]
• Django REST Framework version: [from traceback appears to be recent]
• Python version: [from path appears to be Python 3.x on Windows]

Full Error Log:

[11/Jun/2025 01:10:45] "GET /api/schema/ HTTP/1.1" 500 188110
C:\github\evo-lms-workspace\evo-lms-django\elearning\views\activity_viewsets\assessment_viewset.py: Warning [DiscussionActivityViewSet > AbstractActivityDetailSerializer > AssessmentActivityViewSet]: could not resolve authenticator <class 'common.authentication.WorkflowServiceAuthentication'>. There was no OpenApiAuthenticationExtension registered for that class. Try creating one by subclassing it. Ignoring for now.
...
Internal Server Error: /api/schema/
Traceback (most recent call last):
  ...
  File "C:\Users\somet\miniconda3\Lib\site-packages\rest_framework\serializers.py", line 1067, in get_fields
    raise ValueError(
ValueError: Cannot use ModelSerializer with Abstract Models.