added unit test with parametrize #724 issue

[Scroll07]

Fixes

Fixes #724 by @Scroll07

Description

Added unit tests with pytest.mark.parametrize for media serializers.

• Implemented parametrize tests in test_media_serializers.py based on AudioFactory/MediaFactory structure.
• Covers serializer validations and edge cases for ImageFactory.
• Changes in media_serializers.py for test compatibility.
• Local pytest passes successfully.

Testing Instructions

1. pytest api/test/unit/serializers/test_media_serializers.py -v
2. Verify parametrize runs multiple cases without errors.

Note: CI failed due to environment issues with Elasticsearch, but local tests OK.

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the default branch of the repository (main) or a parent feature branch.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added or updated tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.
• I ran the DAG documentation generator (ov just catalog/generate-docs for catalog PRs) or the media properties generator (ov just catalog/generate-docs media-props for the catalog or ov just api/generate-docs for the API) where applicable.

Developer Certificate of Origin