Add tests for admin.config.create() and config.delete()

[MitulShah1]

admin.config.create() and admin.config.delete() (ferrolabsai/admin/resource.py) are implemented but untested. TestAdminConfig covers get / update / history / rollback only.

What to do

1. Add tests to TestAdminConfig mocking POST /admin/config and DELETE /admin/config.
2. Assert the parsed response dicts.

Pattern to follow

TestAdminConfig.test_update_config.